iCloud storage was never E2EE; the iMessage system was, but not iCloud. As of late last year iCloud can optionally be E2EE, with the "Advanced Data Protection" feature, which is off by default (https://support.apple.com/en-us/HT212520).
I'm pretty sure the point of the concept was to enable E2EE for iCloud storage; that's the narrative I've heard. If it's wrong, well, then it's even stranger if you ask me.
Well they went ahead and shelved the idea and then implemented E2EE for iCloud anyways with advanced data protection so idk how well that idea holds up.