MY PERSONALthoughts on it were that it WAS through intercourse that Ryuko and Satsuki were created, though I doubt that there was real passion in the act. I personally write Ragyo as having a sexual preference for women, though I do place her on the ‘ pansexual ‘ scale in terms of where her sexual orientation lies. ( though she’s clearly aromantic; i don’t see her as being capable of caring for another human being outside of what they can provide for her. ) 

               I think she enjoyed the flattery of a man but she wouldn’t have slept with Isshin unless it were for procreation purposes, hence why there aren’t any children after Ryuko and Satsuki. Ragyo might have foregone or given up those experimentats, and it’s likely that Isshin would no longer submit to the bedroom in order for her to have more children. I DON’T see it as being the same case as with Nui, or anything like that.

                AGAIN! This is unfortunately all speculation, but that’s my interpretation of it, mostly through the flashbacks.