I have studied in psychology, and technically, no person is fully straight or fully gay. There are levels of what are in between the three.
There are people who have accepted that sexually they are attracted to both females and male - so they are bisexual. They ENJOY and gain pleasure from intercourse with a male and female. Not one more than the other, but both. They can also see themselves having a romantic relationship with either sex and feel comfortable and natural.
There are people who basically say HELL NO to intercourse with anyone of the same sex. Not to impress anyone, but because they only feel sexually, emotionally, mentally, and physically attracted to opposite sex partners. They have no want or need to be with the same sex. However, these people can be confused at one point in their lives - usually teen years, but sometimes childhood and adulthood. This is normal, because as humans our hormones don't pick who we want to be with. We can notice an attractive female if we are female - but that doesn't mean we want to have any relationship with one.
Then there are people who absolutely know they are gay. They can't see themselves with the opposite sex - only the same sex. They feel EMOTIONALLY attracred to same sex partners, and want to spend their lives with a same sex partner. However, they can notice an attractive opposite sex partner just as well as a same sex partner. But like I said before, have no wish to be with one.
People can also change their minds. This is someting very common. Usually happens in teen years. In these years, there is a lot of experimentation. One night with a girl can make a girl think she is lesbian forever. Same with males. But upon entering adulthood, they realize what they really want.
So no, I don't believe that bi men are really gay. The chart above doesn't correctly state the question/theory you are stating. I have a chart in my textbook but I don't know where it is and scanning it would be a pain in the ass. Sexual preferences are determined best by the person, and can change over time.