I'm not sure why you would assume the top 28 picks are set. Why, because mock drafts predict it? Last I checked, the guys writing these mocks aren't the ones making the picks.
Secondly, I'm not sure how you chose the 28 players you did. For instance, Bill Walker -- a player you put firmly in your top 28 -- is listed at #34 on nbadraft.net, and #37 on draftexpress. Jason Thompson -- another player in your top 28 -- is listed at #34 on draftexpress, and #25 on nbadraft.net. Courtney Lee is #33 on nbadraft.net, and #22 on draftexpress. For those three players (and I'm sure a couple of others on your list), there doesn't seem to be much of a consensus that at all as to where they'll go.