Hmmm this is interesting because I have the complete opposite problem!
Im a bloke that works in a female dominated field and when I ask to hang out on a weekend with them it’s extremely rare they agree to it or always seem to be busy that weekend.
Genuinely platonic meet up as well. A few of them had to remind they have boyfriends… Like cool sis bring him along too then?
Oh my God just tell him, who cares if you come across as bitchy? If he saw you as a potential romantic partner he’d rather know the truth now. If he figures it out later he’ll think you strung him along and then he’ll really think you’re bitchy.