I think they're just teaching "until ..."—as in, they don't have an "until", it's just "don't have sex." As if sex was exactly equivalent to a drug, where if you avoid the particular subculture that "does" the drug, you'll just never need to think about it.

Though I think the true implication is "don't have sex until an impulse comes along to do so, that is strong enough to completely drown out the voice of your superego in your head. And then—if the impulse really is that strong—the 'proper' order to do things is to get married to that person, and then have sex with them."