To me it makes sense if you account for it being pretty common knowledge prior to the combine that Crabtree and Maclin were better wr's than Heyward-Bey. Then Heyward Bey lit up the 40 at the combine and had pretty good college production and the scouts went off the athleticism instead of the game film.
All year long people said AJ Green was the best WR in this class. He missed 4 games and put up great stats with a true freshman QB where he was really the only guy and everybody doubled him and he still put up big numbers. Yet now after running a good 40 time and looking the part Julio is better? That is crazy to me. If you look at scouting reports on Julio Jones one of the big concerns is his ability to consistently catch the football. That along with the size/speed sounds pretty similar to Heyward-Bey to me.
http://www.mockdraftmania.com/20110228-2011-nfl-draft-julio-jones-scouting-report/
"What separates Green from Jones however is consistency and better hands.
Jones had the tendency to drop seemingly easy catches while at Alabama, as well as allowing balls to come to his body rather than catching with his hands."
http://www.fftoolbox.com/nfl_draft/profile_display.cfm?prospect_id=2744
"
One minor red flag is a propensity for dropped passes"
http://sidelinescouting.com/rankings/wr/julio-jones.shtml
"
Negatives: Inconsistent hands, drops some easy passes, has lapses in concentration... Doesn't always give his best effort, can disappear in games... "
http://www.nepatriotsdraft.com/2010/06/julio-jones-scouting-report.html
Weaknesses:
Inconsistent hands"
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So outside of the combine the general consensus is he is a big fast wide reciever who can make big plays but struggles to catch consistently. Sounds quite a bit like Heyward-Bey to me.