My understanding is that conventional OSes rely on hardware to provide kernel and userspace data isolation, while Theseus relies on Rust compiler, as in safe Rust you can't access arbitrary memory locations.
By "this class of problems" I assumed you were talking about speculation attacks. How does the rust compiler help? Sorry, I'm not going to watch a talk.
I'm sorry, I did not mean that, misunderstanding twice on my part. I meant that you can have a SAS SPL OS and have it safe too. Theseus Book simply states that relying on hardware for data isolation have proven a deficient approach, given the existence of such attacks.
[1] https://www.theseus-os.com/Theseus/book/design/idea.html