they still also know when a specific client with a specific phone number connects to their network
I don’t think so. I didn’t really fully understood how sealed sender worked until now and only trusted Signal to implement it properly. I’m currently reading this which explains how it works and it seems to provide similar guaranties to what I assumed.
The server can only have the IP of the sender. There seem to be some issues, but it’s not as trivial as you seem to think it is. They may also have implemented the mitigations since.
I don’t think so. I didn’t really fully understood how sealed sender worked until now and only trusted Signal to implement it properly. I’m currently reading this which explains how it works and it seems to provide similar guaranties to what I assumed. The server can only have the IP of the sender. There seem to be some issues, but it’s not as trivial as you seem to think it is. They may also have implemented the mitigations since.