One of my former lovers was curious about it, but was absolutely not gay. He loved the idea of that stimulation coming from me. We tried it, he had fun, we moved on.
Trying to define and categorize people's sexuality is pointless. Good, mind blowing sex is whatever you and your partner(s) want to do, and as long as everyone is consenting and of age, it makes no difference WHAT you are doing. In fact, creating trust and comfort, without judgment leads to an amazing carnal experience, physically, mentally, and spiritually. Without it, you're just going through the motions.
I am 200% straight... I adore, even worship good cock. But on numerous occasions, in group settings, I have fucked women. It was what the moment created, and everyone had a great time. Focus on the individuals, not the labels.