I don't buy the whole "returning to the gut" thing. Maybe they mate. But frankly I don't think they move freely from the gut to the tissues. Of course I only have experience with my own situation, but I think that the larvae make their regular circuit, then get stopped somewhere off track. Sometimes where they get stopped is favorable for survival and sometimes it isn't. But once they grow in the the tissues, that is where they end up staying. I mean there is no way these things are moving back through my liver and I don't know about it. No way. They are too big. I also have felt two times over the last ten years, what could have been a worm puncturing my bowel. I've read that there is a place in your colon, low, where they can break through. And it was low like that.
But I do consider that the intestinal track is a closed loop for the adults, for the most part.