Betting handle is but part of the reason why books take larger limits in Pro sports.
College sports sheer numbers, plus talent level variances, allows the sharps and outfits easier spots to step in with strong spot-plays.
As mentioned above, it comes down to the player or outfits specialty for the most part.
But it must be noted that while Shrink's mentor has the ability to win at anything, the likes of BW, Doc M,etc..,clobbered their way to the lion's share of their bankrolls via NCAA Foots and Hoops, by using strong sets of parameters..buying low/selling high.
Also having contacts near and far, in places largely off the map of national beat writers and mainstream tv coverage, in contrast to the Pro's coverage of the 30 largest major metros, and mostly top 25 programs.
This stuff I say is mere ancient street knowledge.