But as long as I had some deep heavy squatting in my program I could never feel as explosive as without any heavy/slow training,
Have you considered that it could be because you're just tired/sore from the weight training? That would be a pretty reasonable explanation without resorting to the claim that weight trianing isn't helpful when it has been the way almost everyone on this forum who has made big gains has come by them.
but there is a reason why in season athletes don't strength train rigorously.
Yeah, because it would fucking tire them out for their practices and matches and add a needless risk of injury. They should have taken care of their strength requirements in off-season.
if someone can explain in depth how to set up a proper program to avoid competing motor patterns I would be delighted to read it.
Read adarq's ratio method post in the performance blog.