a 30% to 40% drop YOY in a stock price, in a commodity price, in almost anything, would be considered a stark drop. Or a crash.

It’s a 30% to 40% decrease in the growth though, not the level. Meta’s headcount will be growing from ~75k to ~81k this year, instead of growing to ~85k. The scenario you’re describing would be more like if Meta’s headcount were dropping from ~75k to ~50k. That would definitely be a stark drop, but that’s not what’s happening.

A 30% drop in year over year growth is not the same as a 30% drop in value.