Generally I agree, Apple tends to undersell the water-resistance on their devices, there are reports of people dropping their iPhones >10m underwater and them still working fine afterwards, or putting their AirPods into the washing machine per accident and them coming out undamaged.
But the Powerbeats 3 were a bit of an exception to this, as there were many people who had them fail on them after a couple months because of extensive sweating, which shouldn't happen so easily on headphones of that price that are advertised as sweat-resistant. They seem to have redesigned them quite a lot with the Powerbeats Pro, and the fact that there is no wire anymore probably also decreased the possible points of failure, so between this and the IPX4 rating, I'm hopeful that they have fixed this weakness with the Powerbeats Pro.