He's very physically gifted -- his quickness and cutting ability are amazing for a guy his size. It's deceptive because he's so big it fools the eye.
Only reason the following is relevant is that you seemed to think he wasn't much of an outlier in the physically gifted department, which is relevant to the question of why BB and Josh might think he's good "project material."
I 'm surprised you didn't look at more than 40 times while you were looking at combine numbers. Tebow's 40 time (while impressive for a 240 lb. quarterback) is not really his strength -- he doesn't really have a "second gear" in that last 20 yards. But 40 time is not the most important thing for a running quarterback, or even a running back. That's why they measure other things for short range quickness and cutting ability.
So before I publish some times, understand this -- Tebow's 3 cone drill is off the charts. His vertical is amazing. His 20 yard and 60 yard shuttle times are very respectable. He is quicker than all those players you listed by any measure, while being heavier and more durable. Did you not know that?
First, three cone drill -- Tebow had a 6.66. To put that in perspective, tiny Ray Rice had a 6.65. And for three years, Tebow was second only to Ray Rice among all RB's and QB's in Three cone drill.
3 Cone Drill
Tebow 6.66
Caparnick 6.85
Newton 6.92
Wilson 6.97
Griffin none
Geno none
Manual 7.08
Luck 6.80
Vertical Leap
Robert Griffin 39
Tebow 38.5 (3rd highest QB at last 4 combines)
Andrew Luck 36
Newton 35
Manual 34
Wilson 34
Kapernick 32.5
(Sort of jumps out -- he's clearly athletically talented.)
60 Yard shuttle
Tebow 11.27
(highest in 7 years of combine for QB)
5th highest in 7 years if you include RB's at combine, just ahead of Doug Martin of Tampa, and Giovannie Bernard of Bengals.
20 yard shuttle
Wilson 4.09
Tebow 4.17
Kaepernik 4.18
Newton 4.18
Luck 4.28