[mrfusion]

Also the first stage might have survived and returned to landing if it had known about the trouble and detached earlier? Or am I misunderstanding?

[lmm]

If the second stage just hadn't been there then the first stage might have survived and landed. But I'm not sure there is any way to "detach early", and you'd have the problem of having too much fuel left over in the first stage. I doubt it's designed to land in those circumstances (why would it be?), so it probably couldn't.

[dabeeeenster]

I think that might be a stretch but I don't think they care about that half as much.