Second part first: you play best against what you practice most against. And you practice most against what your own offense runs. Simply because 1s-versus-1s and 2s-versus-2s scrimmage periods during practices are what they are, and college 'scout teams' are not nearly the self-re-inventing machines that you hope to find in the pros.
So if your own team is a no-huddle zone-read-option spread, and over half the teams you're going to face this season run some version of the spread, that's your defense's strongest suit.
The quirky offense that you're only going to see one time all year (heck, maybe one time every five or ten years!) is not going to be the sweet spot for your D.
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Now the first question: most teams don't run it because there is better out there. The triple-option is not designed to attack fast and score often. It does not take advantage of the entire field, side to side and scrimmage line to goal line. People STOPPED using it because there were new concepts and formations that worked better.
So now that the triple-o is quirky and isolated enough to be effective as a "gimmick," why don't more teams shift back to it to take advantage?
That question, I'm not sure I know the answer to. Seems a few would. For instance, why doesn't Vandy? Or Boston College? It's not like they're having huge success with what they've got (in recruiting or on the field)...why not go for the niche?
*shrug* can't answer that one for you...err, your 'friend', Rat.