I tried to do kelp skip on the old speedrun patch and on low physics and I can get up the slide but it doesn’t trigger the exit prompt at the end. Even when I jump down to start the climb up the octopus and it says to get to the top it will not count.

I am having the same issue.

You won't get the notification popping up on newer versions of the game with the older maps, you must instead listen for the audio cue.