Warren Moon didnt fall through any cracks, he wasnt given a fair shake simply because of the color of his skin
Warner was with Green Bay at a time when they had Favre and liked to develop and possibly trade young QBs but with who was in front of him he never got a chance...to his credit he kept working at it and got another shot
Delhomme was an undrafted free agent of the Saints who spent a year in the world league and eventually signed with Carolina as a free agent
do I really have to mention Flutie again
the point is all of your examples eventually ended up in the NFL because they were good enough to get there and did something once they got the chance and with the way the NFL is always looking for QBs if the Texas Tech guys are good enough they will get their shots but as we all know they are not NFL QBs
monster stats in college does not translate into success in the NFL...thats just common sense