I wholeheartedly agree with you that it's implausible, thinking about Lin getting pregnant without Lisa's involvement. That's kind of the caveat there - there's nothing stopping a heavily pregnant Lisa from convincing her wife to join her in maternal bliss. ;)
I really want to see the MC go up to Cassidy and say "Let's have sex" the screen to go black, and the MC is up a tree due to Cassidy using hypnosis. For the same situation in the kitchen when you try to grope Lisa, but the MC wakes up to an EKG beeping and Lin says, "You propositioned her didn't you? Bad move when she was washing a skillet"