Wow, did not know that. Good thing I am Catholic
Hahah yes a good Catholic who mongers... lmao. Pretty sure Catholics also have a rule about this but hey, why not stick your head in the sand over here with the rest of us, haha.
So I got my answer, as I expected, it's false.
7th commandment says no to adultery. And if you are not married, if you have sexual relations (and again these are strict interpretations) outside of marriage you have to offer to marry or compensate equal to a marriage (i.e. a session fee wouldn't cover this)
It is encouraged that husbands and wives have sex, but sperm is considered sacred and thus should not be spilled unless there is a chance for procreation. A man could have anal sex with his wife, but if he ejaculates, that's against their teachings because it's impossible to get pregnant so thus it's "wasting" the sperm's potential.
Maybe that's where the "it's ok if you don't finish" comes from . But again, it's out of context, and not accurate because technically the sex itself is forbidden outside of marriage, and furthermore - let's be honest - most guys here are married. Which makes mongering adultery by almost any definition out there.
End of the day... people never follow all these rules, they follow what they want and ignore the rest, this happens in all religions, and I would guess, for Orthodox people as well. Although since religion is so much bigger part of their life, probably they follow more rules than most I would imagine.