[css-values-5] What is meant by the distinction between "math function" vs. "function that evaluates to a <number>" #11204
Description
In a few places in CSS Values and Units 5, for instance for media-pogress(), there is a not that reads:
NOTE: media-progress() is not a math function; it’s just a function that evaluates to a
<number>.
Even though I just implemented calc(), and I feel I probably should understand what that means, I don't really understand the distinction being made here.
Are there different behaviors that would be observable if were "a math function"? Different places it could be used?
(cc @tabatkins)