But gender is a social construct? Why should such a meaningless data point have any impact on their bottom line?
The fact that something is a social construct doesn't mean it doesn't matter. Heck, once you get past the basic "keep this biological organism alive" level, most of human life is lived within social constructs. That doesn't meant they're not real or not meaningful.
In a society where someone of the male sex is pressureed to be male gendered there will be a larger correlation between gender and sex. Which would mean miracle balding cures would do better targeting the male gender if they don't have the inofrmation to target the male sex.