The Miami Herald's Jeff Darlington has a nicely nuanced explanation of how and why Tim Tebow ended up committing to play in the Senior Bowl, and it has a lot to do with his new agent, Jimmy Sexton:
You see, Sexton also represents Dolphins coach Tony Sparano and executive vice president of football operations Bill Parcells. That’s the same staff, of course, that created the Wildcat offense. Although less popular, it’s also the same staff that created an NFL-type spread offense that would probably be better suited for Tebow than Pat White.
So not only are you getting a coaching staff that understands how to prepare a player for those types of packages, you’re also going to get a staff far less likely to put Tebow in any jeopardizing situations because of their ties to Sexton.
Ultimately, it's going to be hard for Sexton to keep Tebow from getting dinged by scouts -- they are already inclined to ding him, if only because of the cognitive dissonance from having their recommendations largely be ignored.
But putting Tebow with sympatico coaches allows Team Tebow to live up to Tebow's insistence that he won't be intimidated to perform for the NFL scouts, while mitigating as much of the unknown as possible. You want to have as much of the draft process in your hands as you can.