The movie implies very strongly that Frank Gumm, Vincente Minnelli and Mark Herron were "gay." (Bisexual should really be the term since each of them did have sex with women.) But that's as far as Lorna would go, which was further than she was able to go when she wrote the book.
The rumor repearted in the Gerald Clarke biography is that Judy attempted suicide whenb she found Vincente in bed with a man. But as Lorna herself would say, "How do I know? Was I was in bed with them?"
So yes, Yawper, you are right: Lorna does equivocate on the subject. The homsexuality of these men was similar to the idea of the "down-low" in contemporary African-American community. It doesn't fit neatly into our idea of Out vs. Closeted.