I read a Mystique/Irene fic once where Mystique grew a penis and impregnated Irene, just because she's a shapeshifter and she could. That said, I've not seen anything else. I would agree that since there's no penetration, it's probably not as big, sad as that might be. I mean, in anime, there's "futanari" where one woman grows a penis and that's how the women have sex. It's like this magical ceremony dedicated to peen. And I really don't know why we see A/B/O fic where a woman can (again) grow a penis and impregnate a man, but the same never happens for two women.