Doesn't this make you feel like a mushroom?

I didn't claim "that this was only made possible by cutting back on UV shielding." Those are your words. Though it certainly seems plausible that that is at least a portion of the tradeoff.

As a tradeoff, I am gaining enormously from the greatly increased tread life, and losing nothing to the reduced UV protection, as my tires still get scrapped for tread loss before UV degradation becomes an issue.