I think what they do is somehow invert the penis and stick it up inside, connecting it to the colon. This allows the victim to have, as you say, a franken-gina that can be penetrated as if it was a woman, rather than having to take it up the ass. But they're still really taking it up the ass.

There are so many problems with that mutilation...I've read horror stories that hair grows within the canal, or wound, because hair used to grow on that skin when it was outside of the body.

And what I didn't know but just read above, is that they didn't have enough dick to work with because Jazz had been on puberty blockers, so they had to use stomach lining. Like, what the actual fuck is wrong with our society?