I think American training assumes very regular rotation in a way the vast majority of fighting forces dont have the overehelming material advantages to guarantee.

So the level of tense, professionalized squad tactics you're thought makes sense on a patrol out of and back into a comfortable base, or during a brief raid or something. But this is an all consuming conventional war where Ukraine is at a disadvantage. You dont get rotated and if you do youre still in the field for weeks or months, not hours Dont get to sleep in a safe bed if you do sleep. Even if these people know those tactics you probably cant psychologically sustain them anywhere near as easily. Its too high a state of self induced tension and focus for the amount of time they would be using it.