That couldn't be farther from the truth! If it was the phones wouldn't automatically send all 60fps recording to internal storage to say the least. Even when not recording at max resolution and framerate, the thing still need to be able to keep up with the writes!
Can't go wrong with Sandisk and Samsung. Personally using a 512 Sandisk Extreme in my S 10+ because I do use my camera for recording loads. May be able to go a tier lower if 4K capture isn't on the menu.
Botched and randomly halted recordings say otherwise. And that threshold is a range. These flash chips are not just swappable and the numbers aren't just there for show. There's a reason why Photographers go after compact flash, and pay extra close attention to these speed rating on these things.
It's one thing if YOU aren't hammering the thing, but do not minch and spread false info based off that alone! Even in these phones, and "U3" aside, it DOES make a different depending on use cases.