With all due respect, I don't see the difference. It all boils down to the spiritual maturity of the 2 involved. I quote Paul from 1 Corinthians:
[bible]1 Corinthians 2:14-15[/bible]
If we are spiritually mature, we should be able to reason about this and consider ALL aspects of it before we come to a God-guided decision. It is equally true that love interest is the only difference between having your SO come over just for dinner and having your minister and his family over for dinner, regardless of however many people are home.
I don't see the benefit in overzealous erring on the side of caution when the 2 people involved are sensible people who are spiritually discerning. If they're not, then I agree they need to deeply consider whether such a sitution be entered into, as should all of us. However, the spiritual couple will be able to have in mind firm principles of pure conduct to adhere to.
But in the end it's a personal, case by case decision, and we in our dating relationships need to make a God-guided decision as to what we do in all aspects of the relationship.