Adding some more infos, on all chrome-based browers, but Opera, there's a "bluetooth-internal" page that allows to scan for BLE devices and their services :
But on Opera this page has been removed(?) so i cannot try it.
This page is able to scan devices and their services properly everytime, even when the JS BLE API fails to scan due to "missing authorizations".
Can't really tell what to conclude from this but i thought it was worth mentioning.