While it's a good solution, it is entirely untrue. A message is either End to End Encrypted or it is not. If the message is decrypted at any point between the sender and the intended recipient, it is definitively not End to End Encrypted.
E2EE means it's End-to-End Encrypted. If it's decrypted at any point during transit then it's by definition not E2EE and Beeper shouldn't be making that claim.
It sounds like Beeper on your own server is as close as practical to E2EE as you can get given the circumstances, but the point of the term end-to-end is that there is no, nor is it possible for there to be, any way for it to be unencrypted “except for this one part”. That is the very definition of something that is not end-to-end encrypted.
As someone who works in the tech industry, this is not surprising to me at all. Typically the people who communicate with the media and customers don't know a single thing about tech. They don't know what end to end encryption means. They know just know encryption is involved and they have heard the buzzword, so they repeat it.
Shady service turns out to be insecure and shady. I’m shocked. The real take away from this is if Nothing thought this was a good idea, what other horrible things have they done to their ROM we haven’t found out about yet.