I see what you mean, its a bit weird.
I tested it and it seems that it might be a bug with the platform behavior, I haven't used it a lot, so maybe im wrong.
But if you run the game in debug mode and pickup the green ball then select the player and change Max falling speed to 0 then it stops jumping around.
To me that doesn't seem to work correctly, the green ball being linked to the players imagepoint shouldn't get influenced by the players max falling speed. Also as you change the Max falling speed the green ball actually moves upwards, which again seems wrong to me, in a way that the imagepoint of the player, moves according to the max falling speed.
But as I said I have never really used that behavior so maybe im missing something, that someone that have used it knows. But personally I would make a bug report on it and maybe Ashley can verify if its working as intended or not. But to me it seems like a bug.