Everyone? I wasn’t sure. I doubt a fresh-outta-CSS-bootcamp person would either.

It’s ‘standardized’ within its niche. Niches can have shorthands, but breaking into mainstream seems a bit lofty considering the ambiguity from the outside (I’ve never used regularly) as well as how much & how far you can get with CSS without a library (not saying there’s not obvious places for libraries).

You could be more clear by writing margin-bottom-5, but then you reinvented CSS. And using shorthands for singular properties feels like reinvented CSS—especially since the name implies you can’t even refactor mb-5 { margin-bottom: 6α }. If you can’t use it to refactor, what’s its point?