I’m terribly sorry that I’ve had to dumb down my point so far for people to understand it that you now think it’s yours.
Good day.
It’s both. Phenotyping sex is the common method of determining it because it’s really easy and it’s accurate enough in 99% of cases.
Sexing through genotyping is 100% accurate, but it’s time consuming, comparatively expensive, and only relevant in a tiny handful of cases.