Everyone except Mulder uses Mulder’s body to get laid. That’s even what David Duchovny uses it for.
This is a period of the show when Mulder is openly crushing on Scully and she’s totally oblivious and I cannot get enough of it. That said, this episode gets points off for Scully being exceptionally stupid. It’s not like this is the first inept Mulder doppelganger in your life, Scully.