This is a really cool potion effect! The way it's made is quite unique, and the effect seems helpful.
I'd suggest having this not just apply to falling. For example, it could teleport you out of lava or the void should you fall into those. To balance this, I'd have the duration be the same as slow falling (1:30, 4:00 if extended with redstone) or maybe even less.
I also think the name should be changed. "Potion of rewinding" is a much more fitting name that does a better job of communicating the point of the effect. To be even clearer, the actual status effect could be called "Protective Teleportation".
The optional rule doesn't really make sense. It'd make the potion super confusing โ sometimes it works, but sometimes it does nothing.