Straw men and weasel wording aside, I think that Krstic's personal rebounding numbers aren't as important as the team's rebounding when Krstic is on the floor. The first thing is a decent predictor of the second, but the second thing is what actually happens and what we ultimately care about (speak up otherwise, those who disagree). I mean, hypothetically, if Krstic missed a rebound because he didn't get to it, but we got it anyway because he boxed someone out, that's still a good result.
I don't know what the reality of the situation is (I've missed most of his games with us), and it may well be that he's a big liability for rebounds when on the floor, but I just wanted to point out what I think the important stat is. Although I'll bet that there's not enough data in his small handful of games thus far.
The theory that Pierce will somehow make for the lack of rebounding is one of the most absurd things I've ever read. Pierce is already rebounding above average for his position, his margin to improve is almost non-existent.
Doesn't sound absurd to me; a rebound that Kystic doesn't pick up is one that Pierce might grab. Just do a thought experiment: Pierce playing alongside four of the seven dwarves, vs. Pierce playing alongside four clones of Kevin Love. Now scale it down to one guy, in one position: Krstic.
It's not reasonable to say that Pierce can make up for the gap by himself, but it's reasonable to suggest that he can make an impact on it nonetheless.