I can't remember where I first heard it but here's a few links.

https://www.ewg.org/sunscreen/report/whats-wrong-with-high-s...

https://www.mdacne.com/article/why-spf-30-is-better-than-spf...

This one (https://www.skincancer.org/blog/ask-the-expert-does-a-high-s...) doesn't directly say its better or worse, but alludes to the idea that when you combine the various factors there's definite cons to SPF 50.

Potentially I slightly overstated, what I intended to say was "there's clear reasons why SPF 30 would be preferable in many/most cases". If you are a pale white person who is hiking through the Sahara with no hat SPF 50 might be the way to go.

First link is some political organisation. Second link is a company that sells SPF 30 sunscreen. Third link doesn't even say what you're claiming.