Yes, subpoena was poorly worded. NSL is more likely. But still it is a time-forward threat, which means there is value while the server is or was accepting sealed sender.

And I wasn’t suggesting timing attack is required to defeat sealed sender. I was, on the contrary, pointing out that was a threat even with sealed sender. Though that is non-trivial, especially with CGNAT.

So in summary. You’re right. Sealed sender is not a great solution. But it is a mitigation for the period where those messages are being accepted. A better solution is probably out there. I hope somebody implements it. In the meantime, for somebody who needs that level of metadata privacy, Signal isn’t the solution; maybe cwtch or briar.