Basically: Link needs to be on the ground for the screen to allow a screen transition (and trying to move into the edges is treated as solid). This would accurately replicate the GB Zelda behaviour when using the Roc's feather. Obviously this would not affect sideview gravity screens, because that would break one of the main features of those.
Furthermore: It would make it a lot easier for quest designers to include the Roc items in their quests because they are somewhat exploitable for getting out of bounds or trigger otherwise bad screen transitions. For example: making a jump and screen transitioning over water without the flippers is currently somewhat bad behaviour and puts the player in a somewhat buggy state, this is generally not allowed in Link's Awakening.