Consent is combined with device selection, at least in Chrome.
That leaks at most one bit unless the user selects a device (i.e. whether Web USB is supported or not, as a delayed error due to the user clicking "deny" would be distinguishable from an immediate one), and usually much less since that bit is very correlated with "is Chrome/Chromium-like".
That leaks at most one bit unless the user selects a device (i.e. whether Web USB is supported or not, as a delayed error due to the user clicking "deny" would be distinguishable from an immediate one), and usually much less since that bit is very correlated with "is Chrome/Chromium-like".