You’re right on the composition. The chemical sunscreens also cause cancer, skewing the data and perception around skin cancer. But as long as you’re on a very low PUFA diet and have been for several years (PUFA can take years to clear from the body), then sunscreen is largely unnecessary. The PUFA in the body makes you more likely to burn. Edge exceptions could be if you’re very naturally pale and/or exposed to very high UV for prolonged durations. Ex. I’ve used a tallow-zinc sunscreen, around the summer solstice while outside for 8+ hours.