Erm. I am slightly lost in the memory department these days. But I hope I wasn't imagining the article that suggested some evidence that exchanging saliva actually helped determine attraction to a different gene pool to minimise inbreeding.
That apart, despite being an early bloomer, I still think kissing open-mouthed is rather icky. After 14 years with a wet kisser. It may be an Asian thing like Rachy said. Or it may be a 'some people' thing.
The thing to do is discuss honestly. With boy as well as self.
It may not prove insurmountable. Like drinking red wine on occasion with your friend who likes it though you prefer white. Or sharing a McBurger though you usually eat organic.
Or it may prove some needs are critical to your relationship happiness. Only way to know is to try a few times. Upbringing issues notwithstanding.