It sounds like a specification or implementation bug/feature to me.
That said, it is more complicated to software kill a USB device because a single USB device can have multiple functions. You aren’t killing USB devices by class. You are killing endpoints/interfaces of USB devices by class.
For example, on the computer I am sitting on at the moment, there is a USB device that combines a speaker and a microphone and a volume control. So at the USB level, it shows up, at the very least, as a sound source and a sound sink. If the operating system wanted to kill the source source (the mic), it can’t just disable the whole USB device - and ideally it would kill the mic while ensuring that there was no disruption at all on the speakers.