First off, how is a past relationship a problem for feeling secure in a current relationship? You think every guy you ever meet should have been eternally, completely unattached and should never have experienced attraction before meeting you or they can't love you? That's pretty weird and insecure to be that controlling over someone's romantic history.
Second of all, I don't know if you got the memo, but otome games are games that largely target any woman who wants to read GxB or mostly GxB romances. The men's sexualities, so long as they are interested in women, have literally nothing to do with whether it's an otome or not because characters do not have to be heterosexual to be in a GxB romance. You're just being illogically biphobic and trying to justify it as a preference supported by the genre when it's not. Even if otome were specifically for straight women, which they're not, straight women don't become suddenly not straight by romancing bi men. Give me a break.
Lastly, GL and BL romance games can and do include all kinds of sexualities and genders too. You can't whine about one otome game and then point to a hypothetical situation in different genres which you have backed up with zero evidence or context as proof that you're being victimized because someone wrote something that wasn't about you. If the game has majority GxB, BxB or GxG romances for the player to engage in, it is Otome, BL or GL respectively. Nothing else is relevant to genre definition. It's up to the author and what they want to include. No one has robbed anything from the otome audience by not catering to solely your tastes always. Stop being entitled.