...and it doesn't use mass storage at all, blocking access to it in a clunky way to prevent simultaneous usage.

UMS seems like a nice idea when you first hear about it, but it doesn't really offer much once you look at it closer. The only proper argument for it is "no special software needed", but it a world where picotool is `apt install picotool` away that's not very advantageous anyway and only causes automount annoyances.

UMS shines where you have a device with a filesystem in its flash that you can access to actually manage the files stored there. Super useful for stuff like MicroPython. In contrast, pseudo-mass storage like on RP2040 doesn't seem very useful at all. It makes it appear more approachable, but only superficially.

The whole UF2 idea has to do with the educational background of RaspberryPi. The protocol was invented by Microsoft for use in some kind of similar educational board with the express purpose of not needing drivers, being reasonably crossplatform and crucially not needing any special permissions to access the device. The end result is that in some kind of educational setting you can use some kind of cloud/remote IDE on iPad, stick the RPi-Pico into the iPad and flash it, no blessing from Apple needed.

Oh. So it's just a result of locked-down walled gardens being so widespread that they influence the world around them. Depressing, but thank you for pointing it out anyway; on my phone I can just run picotool itself and it's easy to forget how dystopian it all got outside of the niche I'm in.