Adaptive AI is definitely real. They use the variable performance (the "catch up" AI in terms of temporarily boosting speed amongst other things) to attempt to make the games have "realistic" outcomes. I'm like you in that i dislike using sliders and try to do as little of it as possible until it's the only choice.
The problem, as you're discovering, is that the sliders don't fix the issue because it's not an across the board thing. The CPU just does it when it needs to. The problem with using the Acceleration slider (which DOES work) is that it also gives you an advantage at those other times when the CPU isn't getting temporary boosts. You'll likely find you have too large of an advantage in those situations.
Ultimately, this is why sliders are a poor choice for game balance. Balance one aspect and you throw off another. Some issues come through (like GK Ability) no matter what the slider is set to, even when it's 0. To answer your question, no, there isn't a setting you can change. People abused running down the wings because it was so effective in years past that EA just took away your ability to do it instead of fixing the core issue.
Best FIFA I've personally ever played - just have to suspend disbelief and accept that most CBs can run down your wingers.