Everything on the spectrum of human experience is a spectrum, there are no real black and whites in real life. Actually let me rephrase that - everything in the spectrum of human psychology is shades of grey. There are obviously black and whites like someone having arms - OR NOT - or having a Y chromosome, OR NOT.
Sexuality however is not nearly so concrete, and I'm curious why anyone would try to insist that it is. The obvious challenge to this claim is that it's quite possible for a man to look convincingly enough like a woman that they are attractive to otherwise straight men, and vice versa.
There is no-one who is so "totes straight" that they couldn't be "fooled" into being attracted to someone other than their preferred gender, and anyone who claims otherwise, is, IMO, somewhat in denial, perhaps about their own sexual preferences.