After testing, I can confirm that being on a higher framerate can result in faster ladder climbing speed and possibly other advantageous behaviour. This doesn't affect speedruns, but an example of other advantageous behaviour from high fps is that lava moves slower when your fps is high and faster when it's lower.

TL;DR, I think there should be a rule where everyone has to run on the same framerate (60 is a good number as I believe the game was built around 60 fps).