Tricking someone pretending you're the gender you're not is uncool at best and downright nasty at worst. In a romantic fantasy where a happy end is the iron-set goal, the fooled one, after the reveal, will always decide they don't care about gender anymore because love is more important. But in any minimally realistic setting this treachery will hurt the victim horribly and bring only heartbreak and bitterness.
And just like the brown girl said, "there's no smoke without fire". In the lesbian confession page in my country, there's always some girl who cries about her bi-girlfriend dumped her for a man. Heck, in 1 case even a bi girl complained about that. You can't deny the fact that bisexual girls earned themself a bad reputation