> I’m in my early 30s and am starting to think about getting a screening.

This is a pretty stupid thing to do unless you've had some sort of symptom or family history. Your protection from illness due to screening is statistical, and jumping out of the calculated recommendation just makes it more likely to hurt you (false positives, false negatives, injuries from the procedure) than to benefit you.

Desperately trying to fabricate a reason is just intentionally trying to hurt yourself.

I'm not against colonoscopies (is anyone?) and I personally had my first one early because of an odd pain. Turned out to be unrelated.

edit: the neurotic desperation for disease screening that I see in a lot of people bothers me a lot because it's this odd fetishization of medical science combined with the active subversion of it. For me it's a weird insistence that all tests are good but that the math behind them is not.