I think the facts is that you never really wanted to limit yourself to "tall" or "wide" but just average , the game (before beta) pushed for you to reach a balance of productivity/research-unity inflation and then start to vassalize to switch completely to specialist tier jobs while sucking the basic resources from other empires.
The beta is still to young for me to come to a conclusion, for now, IT FEELS different in your capacity to improve your production with enough efficiency to balance out your inflation, so just keep growing doesn't seems to have malus at all. At the same time, investing your alloys in something that is not map panting, still feel somewhat rewarding and offer a "tall" growth, but you still need to go towards vassalization to complete your growth.
In the beta or before i don't think simply going "tall" without vassals was ever a "competitive" action, as such you can always go tall,it is just not going to be efficient, like always was.