Speaking as a genetic female with no hormonal imbalances (and pre-HRT), I have a happy trail that goes up to my chest. It's wiry under my belly button but softer and shorter like the hair on my arms the rest of the way up, until it hits my chest hair (of which I have about a dozen). My hair is black/brown so it's very apparent even from a distance. It's not uncommon at all for cis-women to have at least a little trail, and not odd for some cis-men to lack one. The presence or absence of a happy trail would never cause me to question someone's gender, personally.
