This is true, most of 320kbps is indistinguishable, but high hats are often subject to artifacts, including pre-noise that occurs before the sound is supposed to begin. To some it might sound intentional, like a very subtle reverse high hat or other room effect.

This and also transients - they sound in a specific way through the way the compression works. Once you hear it, it is difficult to stop paying attention to it.

Right, high hats are a source of transients which get smeared because there’s a minimum block size in mp3 that is somehow too big to encode it temporally.