> it enables a way for people to scroll up to see every note they missed since last session. Is this necessarily a good thing? To me this is stressful,

Interesting take.

But it could also be stressful for someone to go back through the history to look for the last notes viewed, and then jump back to the top.

I think we can find a middle ground and it dependes from the context: in a general feed (followed) is probably healtier let the notes flow; in a curated custom feed with a moderate flow I would like to keep the sign of where I was at.

Perhaps an option for each individual feed is the right choice.