[Fluorescence]

> someone high up

Has to be. It has that Musky smell of banning yellow safety paint i.e. too stupid to be a team effort.

Legibility issues with translucency is such a basic thing and I expect Apple designers have gone deep on the topic e.g. mathematical models using human colour perception to determine hard limits for different type weights. I don't think the heavy frosting in past versions was an accident.