You only consider "every move immediately loses". What if every move loses, but not necessarily immediately?
Also, it's not clear what "S!" means and where the contradiction is.
Well why didn't you say and ask that right away? And why don't you say why you doubt it's correct? I think that would be more useful than making this a game of "what could he mean?". It's also not clear how your question differs from this previous one (other than being that game).
Looks like your connection to LeetCode Discuss was lost, please wait while we try to reconnect.