Kink, fantasy, role play, BDSM, all of that factors in. It's destructive when one person wants that stuff and feels they have to repress it. That can lead to cheating, porn addictions, secret sex workers, and even SA (against the partner or sometimes somebody else.)
Saying "Yeah, I think I'll like that" or "That'll be OK" ahead of marriage isn't the same as living the marriage and doing those things. You don't know what they'll feel like until they happen. It's not just the same as masturbating or imagining it. Our bodies have minds of their own.
Another important factor is sex drive. You'll both likely be horny and roaring to go, prior to marriage. You're imagining this elusive thing and how great it will be to "connect". That excitement or curiosity doesn't always last. The novelty can wear off quickly. Women's hormones in particular can change from taking oral contraception, from IUDs with hormones, with pregnancy, breastfeeding, and postpartum fluctuations, from menopause, and any other type of physical reasons. Men's hormones can change too, but with women it's much more obvious and women often take the blame for this.
There's a lot to consider when deciding if someone is compatible. It's just as complicated as figuring out if someone is compatible for marriage, with comparable ideals about finance, spending habits, housework, and all that other boring stuff.
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And in the end, the love you take is equal to the love you make.