Very hard for WRs to adjust to a spread option style attack. As the passes are not "anticipation" passes like the NFL style WRs are used to but instead sight based. Where as say Brady will throw the ball where the thinks the receiver is on the route. (the timing) to know his WRs. With Tebow and the spread style option the QB even in the pass formation is looking at the other options and not waiting for a receiver to get in a spot but rather become open. Tebow is not a pro-style passer he is a sight passer.
Where as Most NFL Qbs are anticipation passers and like today Brady over threw 85 by a long shot because he was thinking he was going to run the straight route, but cut back instead. So while it was not a bad throw by Brady per say as he threw the route, his receiver had stopped and came back and was wide open.
The timing comes into play when the receivers are not used to this style of play and while they are expecting things to happen at certain points in the routes often times Tebow holds back or throws to fast when he sees the opening. Not when the route is at its pass point.