That might be part of it. I also think that they tend to focus more on the guy they're matching up against, and they sometimes forget to run back and help cover for their teammates.
with Van Gundy after someone shot it, 5 guys would trot back, but with Adelman when someone shoots it, 1 or 2 guys go for the offensive rebound. our transition D is going to be bad when T-Mac looks slower than Yao out there.