Sex doesn’t imply exclusivity either. If you only want to have sex in an exclusive relationship, it’s up to you to make that clear.
It doesn’t matter how far I or anybody else might go with each date. It only matters what YOU want to do. If some schmoe expects sex by whatever # date, and you’re not ready, that’s his problem, not yours.
The best time to have sexual in a relationship is when you both want to.
I’ve heard good arguments for not rushing things with someone you regard as a potential serious prospect. But if your willing to accept the risk that the relationship becomes pretty sexually focused and may not evolve beyond that, go for it whenever it seems right. Indeed, it might be good to find a friend to blow off steam with so your head is clear with the people you’d like to get serious with.
Keep on setting us up with straight lines like this!