I figured it out, if you use the Magic Strapon no checks are made on you (which doesn't really make sense) as soon as I used Phantasmal Cock with Phantasmal Seed unlocked Felicia can get you pregnant.
Ahhhh... yeah. Similar issues to the condoms really (it was checking the genitals selected for the scene if they blocked pregnancy checks, regardless if they were the relevant genitals, as this is the only scene that involves multiple player orifices currently), hadn't thought about that. The fix I used for the condoms should work for the strap-on issue too. It will probably go live somewhere after Christmas.