This has become more obvious the more that I've played the game. As an example you can see for yourself, start a normal single player custom game as Leon and then as Galicia.
What you'll find is that if you declare war on Galicia, even in the first month or so, their army will far outnumber yours as Leon. Two to one in troop numbers, especially if they have an alliance with Gwennyd (which is out of diplomatic range/impossible to ally with if you actually play as Galicia, by the way.) Even if they don't have an alliance, they have higher numbers than you. They even have higher numbers than you if Portuscale rebels and you declare war then - higher numbers when they only have four counties? Really? Hmmm....
If you then play as Galicia, Leon will attack you within the first month or two, with a 4-5k troop stack (no alliances necessary.) The best you can muster as Leon in the first month is 2.5k. The best you'll muster as Galicia is about 2k - Leon totally wipes the floor with you and vassalizes you.
If Paradox wants to make extremely difficult games, fine. But I want a fucking ticker option to make sure that the AI is playing by the same rules and can't just conjure up double the troop numbers I could from the same situation. If I can't get a ticker option for that, then I guess I have to assume playing this game on 'ironman' is more or less a joke. I have to believe that using console commands to cheat myself a mercenary army is the way I'm 'supposed' to play the game - since everyone else seems to be able to conjure up thousands of troops out of nothing.
For a really great example of AI cheatery, I was doing a Leon run (cheating this time) and I had taken over about half of Espania. I was attacked by a muslim Jihad that resulted in 15k troop stacks being sent my way about every month, for about 5 years straight. This is only about 50 years after a no-dlc game start from the earliest available period.