Nice powers of observation.
I don’t like full-on intercourse with people who I don’t have an emotional connection with. I consider sex to be a pretty vulnerable thing (as much as it can be fun and sexy and silly) and I want there to be a strong degree of trust there, whether the person is a primary or a secondary partner.
If you want to call it intimacy issues, go ahead. But it’s just my preference.
Also, intercourse is just kind of boring and redundant to write about in general. Scissoring is kind of just scissoring until it’s not scissoring. A penis entering and exiting a vagina can only be described in so many words before it gets hokey.