> count undo as a partial game over

Not at all. Contrary to other games where undos are cheating, here they are part of the game. Without them it would be 80% luck and only 20% strategy.

> which is heavily implied

I can't find anything that implies this. It explicitly says:

> This uses undos deliberately rather than only as an emergency

while avoiding undos is mentioned at the end as "The Purist approach", which I read as slightly mocking.

I see it like a chess problem where you have to find the best sequence of moves, so you start off with an intial move, then backtrack, explore another idea, etc. Not like a chess match where of course you cannot undo any move.