Are you claiming that Mullvad are doing the same for the Firefox-brand VPN? If not why are you making a distinction between email,matrix and vpn services?
I chose those services based on the list in the parent’s post only; I could have filled in any service where the provider hosts your data on storage for you (eg. Usenet, RSS feedreader, web forum, file sharing).
I don’t consider VPNs to be a service that host the data you interact with on their own storage, so they aren’t of interest to my question.