if some people in China are trying to get around the censorship.
First, it's not just some people. You will find Steam, UPlay, GoG all have a great Chinese player base. Especially on Steam, Chinese user number once surpassed US user number and achieved the top place in the world. (Currently, still on 2nd place.)
Second, it's not a get around. It's our righteous right to visit those stores and spend our money. The censorship is technically illegal.
According to law "Any ISPs has no right to block users from visiting certain sites of internet."
and according to constitution "Citizen's communication, including mails, phonecalls, internet connection is private and shall not be monitored unless under police investigation."
PDX needs legal certainty about the fate of its investments
Legal certainty is what I have provided.
The law of China acknowledges all international agreements China has signed -> China signed WTO agreement -> WTO agreement clearly allows people in China to buy games directly from foreign online stores which is outside China's jurisdiction.
That's basically the foundation of why Chinese people can buy games from Steam/GOG/UPlay/HumbleStore or any foreign online stores
A game focused exclusively on China will be expected to get at least a good chunk of revenue from China
Why?
Koei's Romance of Three Kingdoms and Dynasty Warriors got most of their revenue outside mainland China before they have Chinese localization.
I'd expect the same on the incoming Total War.
There is no direct connection between contents focus on China and the revenue from China.
You will find Chinese players spend stupid high amount of money on Japanese anime games. So, if you expect to get good revenue from China. You can make something like this instead.
To Paradox fans in China, we just buy whatever there is a Paradox strategy game tag. We don't care if it's Roma, it's Britain, it's some countries we never heard of. Give us a store link. You will find people rush to hit the buy button. (A recent example is MtG, before steam removed the regional lock on DLC, many just jump onto Paradox store to buy it.)
We are grateful to just have anything like this we can play even it can be buggy as hell. Because so far as we know Paradox is not going to abandon us while many other companies just applied their regional locks to China. (Likely, under some bad influence

)
Many Chinese people are very very easy to be satisfied. They will not even complain about working 80 hours a week while I am a quite lazy person.

When there is a bug found in Paradox games, local communities in China will just try to mod it out and carry on silently. (Maybe you will find me being the only Chinese player bouncing around Paradox forum. And then, think about China's player population based on Steam sales data... There may be like hundred thousands of silent Chinese players.)
to remove any possibility of a ban
OK, let's not talk about "ban". It may be too complex. It's talk about to get approved.
Here is some pre-requirement to get China start to even consider the game to be approved:
1, All online chat must apply language filter to avoid "sensitive words" that may be against government policy. All the chats during multiplayer game must be logged.(Well, many games just remove their chat function in China because of this.)
2, All servers must be located in China, including those servers host by players.(So, anyone hosts the game is inside China's jurisdiction. If government find you are doing something illegal in game, they can just kick your door. Check CS:GO....)
3, Either the developer or the publisher must be a company in China. (So that government can find someone to punish if things went wrong. Our friendly neighborhood Tencent is super willingly to be you partner...for a price.)
4, No games shall actively encourage PVP ( Tencent tried quite hard, but PLAYERUNKNOWN'S BATTLEGROUNDS is never approved. But, Chinese people are flooding steam server anyway.)
5, No liquid of any color shall be displayed during any fight. (Previously, only red blood was not allowed. Now any color is not allowed. You will never going to see fallout 2/Mortal Kombat gets approved anyway) Death of any character shall be avoided. (Didn't we kill millions of people in HOI4?)
6, You will need to send 2 hard copies of the game on DVD to apply for approve. Whenever an update is made, you will need to send 2 hard copies of latest version of the game on DVD to get approved again. (WoW's Chinese server is thus always lag for 6 months compare to international server.)
7, You will need to send your source code too if authority asks. (Of course, that makes China can acquire your technology which Trump recently found untolerable

)
8, Female characters are not allowed to wear clothes cover too little skins. (No DoA anyway....)
9, It will take months for government to decide if approve or not AFTER receive all the applying materials from your partner in China. (Take a nap.

)
Now, let's talk about investment. Despite all the political stuffs. How many companies want to play according to those rules above?
That's why only just a few ten-thousands of games got approved during last a few decades. more than 90% of them are just trash mobile games made in China, those cheap card/chess games are everywhere. You can almost never see any 3A games on the approved list.
If your "ban" is equal to "not approved" then most of games all over the world are "banned" in China indeed. (Most of them didn't apply to be approved to begin with,as quite few will hire a partner in China.) Thus, I see nothing special about HOI4. If it can be a reason to remove games on Steam. Then, maybe we may have like 10 games left on Steam.
Conclusion: why bother to appease China's government?
A game or DLC heavily about China shall be targeting to the players all over the world just like other games/dlcs.
Did Paradox's old shogun game expected heavy revenue from Japan? I think not based on steamdb sales data.
Did Stellaris expected revenue from alien creatures many light years away yet to be discovered by us? Absolutely not.
It's just like China's Kung Fu movies are mostly viewed by foreigners. People in China much more prefer those magic-like fantasy Wu Xia movies instead.
It's just like some "Chinese food" are only made for foreigners.