Okay, fine, there are a few other proposals regarding information about or control over the local device that Mozilla disapproves of on similar grounds. But it still comes down to "We don't think users can ever understand the security risks involved with this kind of access", which I've abbreviated as "users are too dumb". You can argue that "they're not dumb, they're just human/inattentive/fatigued by warnings/whatever", but it still comes down to having the knowledge or not. (After all, if it were just "We don't want a single click to give immediate access", they could just make the prompt/warning harder to mindlessly click through.)
Of course, the alternative to the user getting a browser prompt to communicate with their USB device is for the user to download a program to communicate with their USB device. So if they're set on doing whatever they are attempting to do, then it's not like they can ever avoid the risk of threats they don't understand, since desktop sandboxing is still mostly nonexistent.
Stop projecting your own view of users on what Mozilla is saying.
> Of course, the alternative to the user getting a browser prompt to communicate with their USB device
It's amazing you write this literally after I wrote "Why do people in these discussions pretend that it is only WebUSB that needs a permission and consent?"
It's not only WebUSB that requires user permission, but it is only USB/serial access where Mozilla has decided that a permission prompt is inadequate.