When I was growing up, my grandparents still had an
outhouse on the farm. We'd go visit them and due to the shallow, inadequate septic system, they'd encourage us to use the outhouse rather than the toilet in the house. That was when I was first introduced to black soldier flies. People called them "privy flies" because you'd see thing when you sat down in the outhouse to do your business.
No one was at all concerned about BSF spreading pathogens or anything like that. Once they pupate and fly, they don't even have a mouth so they can't bite anything --- all they do is lay their eggs and die. The only time in the BSF lifespan that they'd be in touch with
poop was while they are larva/maggots. I'm not sure how they'd even come into contact with the feces and spread it to another surface.
On the other hand, regular houseflies do that all the time. They'll
land on the feces and then land on your potato salad. BSF, once they colonize an outhouse (or any other food source) are hell on any other species. They keep other flies from multiplying in the outhouse. They're your friend.
For these reasons, I think you're OK.