I kinda remember that the counterargument Google used is that only devices with a special attribute would ever be available through WebHID, ensuring that such older devices would never be exposed.
Cue my surprise when it turns out you can use WebHID to program a Minidisc / Net-MD device [1], so.. they never did implement that filter, apparently. I mean, certainly it is useful, but ... What The F., Google?
The user has to first specifically pick the device from the list and grant the website access. If a user is confused by a permissions prompt and has no idea what is going on, the default path is to reject the permission.