Is the reverse true as well? Unusual preferences can lead to lonliness?

Seems logical. If you're into medieval re-enactments, you'll have a much harder time connecting with people than being into the NFL. It'll be a blast once you find that group, but you're finding a needle in a haystack.

It's a bit why there's common advice (that I'm ambivalent on) in "if you're lonely, get a dog". Not just for the social factor, but because dogs are an almost universally loved pet and instant icebreaker for other pet owners or pet lovers. that first step to socialization is harder than ever.

only if you aren't keen to share them with your friends.

if you watch an obscure show or movie or read a rare book, most people will be eager to share it with their friends, and their friends will be eager to learn about it. It's not the preferences or experiences that make you lonely, it's whether you trust your friends enough to share them.

truly, nothing is more fun than finding a cool movie and then showing your pals, who then also love it. That's the best!