Why not just create a 5th variable type? Color, Number, String, Boolean, +Percentage+

I’m sure a lot of people know if they want px-based or a percent-based values to adjust their line height and letter spacing. If “Percentage” was a variable option, then I’d just have chosen it the first time set up all my typography variables for letter spacing. I was surprised when I applied the variables that I carefully planned out to my text and it didn’t space the text as I expected. So, why can’t Figma just introduce a fifth type of variable option that is just for specific percentages when you click “+ Create variable”??