Isn't it fair to say that this brings Zoom more-or-less exactly in line with the privacy vs law enforcement balance of a normal telephone call?

Writing from the UK, I'm reasonably sure that (a) all my phone calls are not recorded and (b) the phone number and duration of every call absolutely is recorded (this has to be shown on your phone bill!) and is available to the police when needed.

Speculating further, with the right court orders / warrants the normal E2E encryption algorithm for a particular user could be replaced with a "law enforcement decryptable" one and, hey presto, it's a Zoom equivalent of a proportionate wiretap that only covers future calls. Certainly a lot better than encrypting the calls of all users with such an algorithm "just in case".