Ok, some physics on this.. initial assumption, that they all fall at same speed and that they fall through an atmosphere, which causes drag.

There's the weird question of how different shapes and sizes, at same speed, yield comparable drags, but let's leave these kind of questions and accept it.

Issues/quirks: if you jump from the border os the island, you will most likely shoot up, not fall. Actually, bear the edges, there would be a lot of turbulence, so, depending on the size of the island even reaching the edge would be mad.

If you make a jump, you won't fall back, except if someone pulls you down or if you can hit so a thing above you and "jump negatively" to suffer an extra force siwnwards.