Anon for obvious reasons
I've spent quite a bit of time on Adult FriendFinder for many years since it started about 20 years ago and I've met a lot of people - you need to actually experience this because academics doesn't work. Since AFF is an adult site and you end up enjoying "adult" activities with the other sex (at least initially) when you are sitting there with no clothes on conversations are generally quite honest ... most couples that I meet are very happy to start off with M-F sex but very quickly slide over to M-M, F-F, M-F-M and F-M-F sex.
Are they "gay" or are they "straight"? Fact is, when you get down to it, pleasure comes first, orientation is secondary - most guys enjoy watching and playing with people involved in F-F sex and virtually every woman I've ever met has been very keen on watching and encouraging M-M sex and helping.
Of course nobody would ever admit this in a survey.