In the game i run, there's a percentage counter for collectables, but there are also some required items that can be skipped. I typically think of the name "low%" as collecting the least amount of items, so would low% mean "minimum items", or would it be taken more literally as "0%"?
0% would probably only apply if it's possible to actually complete the game without collecting anything Otherwise, "Low%" would be whatever the lowest possible item percentage it
Plus if you can see the percentage going up and you know that skipping certain items keeps that percentage low, then it should be pretty easy to determine the lowest possible percentage you complete the game with, and then you don’t need to call it a generic “Low%” and you can actually call it after the explicit percentage (kinda like how Metroid Prime has 21%).
Of course if that lowest percentage is also the fastest way to complete the game, then, well, you just have Any% and it’s moot anyway.
If your game has an actual in-game numerical % counter, I'd ditch the name "Low%" and name the category after the actual lowest possible percent. If more skips get found later and a still lower % becomes possible, you can always make another category.
If the game you run can make you accidentally do an optional action that increases the percentage, I don't think Low% would be suitable for it. In this case, you could go for something else instead like No Upgrades etc.