WebExtensions were already practically required to be a superset of Chrome's APIs, so the incentive is already there to just use what Chrome offers for maximum compatibility. Mozilla can and does offer additional APIs beyond what Chrome does, and in some cases (like adblocking in a manifest v3 world), this will soon be more relevant as Chrome's adblocking capabilities will take a hit upon killing manifest v2, but it's already the case that Firefox is a better platform for adblockers, as detailed by uBlock origin devs: https://github.com/gorhill/uBlock/wiki/uBlock-Origin-works-b...
I don't see this group constraining vendors to implement _only_ the blessed APIs, much like web standards hasn't stopped Chrome inventing new APIs for Google needs.
WebExtensions were already practically required to be a superset of Chrome's APIs, so the incentive is already there to just use what Chrome offers for maximum compatibility. Mozilla can and does offer additional APIs beyond what Chrome does, and in some cases (like adblocking in a manifest v3 world), this will soon be more relevant as Chrome's adblocking capabilities will take a hit upon killing manifest v2, but it's already the case that Firefox is a better platform for adblockers, as detailed by uBlock origin devs: https://github.com/gorhill/uBlock/wiki/uBlock-Origin-works-b...
I don't see this group constraining vendors to implement _only_ the blessed APIs, much like web standards hasn't stopped Chrome inventing new APIs for Google needs.