I don't disagree, but I think there is a distinction between "everything is e2ee, but specific conversations may be MiTM without detection" and "nothing is e2ee and can be retrospectively inspected at will" that goes a little beyond security theatre - makes it more analogous to old fashioned wiretaps in my mind.
Obviously it involves trust that it isn't actually "we say it's e2ee but actually we also MiTM every conversation"
Even with closed source clients, MitMing every conversation would likely be detected by some academic soon enough - various people take memory dumps of clients etc and someone would flag it up soon enough.
Obviously it involves trust that it isn't actually "we say it's e2ee but actually we also MiTM every conversation"