I feel like that sort of expression encourages biphobia; even if 'genuine' (whatever that means) bi people are rare, an expression like "Bi now, gay later" perfectly plays into long lasting tropes such as bisexuality being "just a phase", something which bisexuals such as myself have spent a long time trying to overcome.

To add on that, studies like the ones mentioned only reveal so much; there are a few good reasons why one might only search for one gender or the other online and in a particular place.