It looks very connected to me @Daniel_Wilson. I think your query
is not returning the expected value because expand(_all_) @filter(...) does not follow the reverse edge from B to C. And it should.
I have created a repro case in postman and added it to the issue. I also set the kind/bug as we should either have expand(_all_) @filter(...) working or at least we should prevent user from declaring the reverse relationship in the Type definition. (As you know, expand(all) is using the Type definition).
Let’s see what our engineering can do. Thanks for the use case details.