Interesting! I hadn’t heard about this. This would make it so that Signal could say that they don’t know the message pair.

Have a look at what they reply to subpoenas with.

https://signal.org/bigbrother/cd-california-grand-jury/

This is just a marketing gimmick, it's been broken as a technology since its inception: https://www.ndss-symposium.org/ndss-paper/improving-signals-...