To me it just sounds like they encrypt the seed with your proton keys and then decrypt it when using their webui.
They probably store the xpub (which is fine, for most people) tho because otherwise I have no idea how their send bitcoin via email functionality works
that's a lot of "sounds like" and "probably"s xD
Oh for sure! I have no insider information whatsoever; i just like what proton does as a company so I give them the benefit of the doubt. Perhaps I shouldn't, but until I'm presented with any information that makes me not trust them I will cautiously trust them, tho you're right that page should be rewritten to be more clear.
