Problem is that now you have to compare these heights to all the other NBA players. 6'8'' (Williams) might be a normal size for a center now.
Honestly, nothing on this list surprised me that much.
I've always felt that standing reach and core strength were more important criteria for "size." I say standing reach because some NBA players have really long arms and high shoulders, and other don't. That let's you get more vertical. I say core strength because you have to be able to take impact and keep your arms up to defend shots.