But PNAS published a bad and stupid paper just to make sure.
Senior author, J. Michael Bailey, has a record of transphobia and terrible research practices, including using off-the-record conversations in studies. Steven Pinker, academia's enfant connard, who for some reason was allowed to be the paper's editor, has a history of supporting Bailey.
Anyway this is stupid and ludicrous. It's bad science to strip away social context from the questions you want to ask. It's straight up hateful to look at obviously common human behavior, test whether it exists, and treat it like a pathology. It's not for a laboratory scientist to say whether the way a human behaves is real. Take the very first sentence from the abstract as an example:
The question whether some men have a bisexual orientation—that is, whether they are substantially sexually aroused and attracted to both sexes—has remained controversial among both scientists and laypersons.
That's not true at all! This is just making up out of thin air a reason to subject people to invasive and personal questioning. Why is getting a statistically significant erection the standard for whether something can be said to exist? Bisexual men exist because there are men who are bisexual.
Social scientist Dan Simpson said it best:
Imagine saying “the indium/gallium strain gauge I hooked up to this man’s penis didn’t show consistent arousal as I Clockwork Orange’d him with gender-spanning porn, so male bisexuality does not exist”.