I don't think there's a causal relationship. Garnett was once the best rebounder in the league... years before he was coached by Clifford Ray. Bass was always a poor rebounder, O'Neal declined from good to mediocre years ago (after the injuries), Wilcox is rebounding at his career average. It's just a collection of average and poor rebounders and Pierce/Ray Allen are too old to make up for that. They used to be above average rebounders for their positions... not any more.
Maybe the Celtics should rehire him or hire a new big man coach, but the only big in this roster that may stay here long term is JaJuan Johnson and he isn't a typical big man anyway.
Danny's reluctance in addressing the rebounding issue has always irked me. The team has struggled to rebound the ball since the Garnett/Powe injuries.