I really hope he did find out, or at least had a good theory, on what protocol stack Starlink runs on. The engineering achievement is amazing, but it's sad that it all seems to happen entirely behind closed doors.
https://blog.apnic.net/2024/05/17/a-transport-protocols-view... is the best resource on its channel properties I've seen so far, but it's all empirical.
I know Dave was still trying to figure out exactly how Starlink worked, and how he could help with its performance characteristics, at least two years after that talk, as he sent me a draft of a document related to that.