I agree with a lot of what you said in regards to the CPU adapting to the game situation and match scenario. It is a script, but scripted is a bit of a loose/generalization that seems to serve more as something to blame versus actually seeing an abnormality in animation.
The D-Pad has little to do with animations however. You can go into defensive, balanced, all out attack, and the animations remain the same. It's more so the intent of the players on the field - and then the slider modifications compliment that intent. If you have a height of 100/100 and go all out attack, then you will be sure to find the midfield extremely cramped and you will see runs being cut off sooner than they would if the height was at 50.
I do agree that there is a rubberband effect of the CPU acknowledging the user's choice and then combatting that though. However, sliders aren't just geared for match scenario as that is just one element of the advantage of using them - but as you know in this sport, every inch matters, and essentially that is what sliders can achieve. It can make the difference of those inches and modify a behavior. So while "us guys" are obsessed, or so it seems, there is a lot of validity into why we choose to be.