Oooh, I remembr that. They did talk about that in the Tinto Talks. It has nothing to do with the limit force. It is a minimum size your country is expected to have in army, not a maximum. I guess it is a mechanic done so you cannot cheat the AI and have smaller armies than you should from your income and save too much money. Also possibly to force the AI to always have a decent army size.
Im not super keen on it but it is not terrible either
