I’ve seen keyboards that allow firmware upgrades & configuration over WebUSB. This covers not just Linux but even smaller OSs as well as the audience using Android tablets as a PC or whatever.
WebMIDI is also a boon for anybody working with external audio gear on Linux, some companies like Novation went all in and provide web-based firmware updaters and configuration tools. For other gear I still need to boot up a Windows VM and fiddle with USB forwarding.
The permission prompt in Firefox is definitely sensible though (especially for SysEx), not sure if Chrome added that as well.
Google themselves use it for updating Android devices, via making an ADB connection from their update webpage.
I don't see how it could be classified as hostile, as it's adding a feature rather than taking features away.