Since it was a clinical study, they have to be upfront about the sample used in testing. Since it's a drug for an STI, then they have to be upfront that they only tested the drug with people who had partners of the opposite sex. It's only relevant if someone else comes along and runs a similar test and finds different results, and this way the company can say "The differences might be because we only tested it in heterosexual couples, what did you use?"

Just the rules of research.