To me, that looks like a fix for Carelessly splitting a solved post to a new topic breaks things
It doesn’t seem to fix the problem described in the OP which talks about a whole topic being moved to another category where solutions aren’t enabled, not about moving a few posts to another topic. When I move `personal_messages:username` search filter doesn't work, which is a solved topic, to Feature where solutions are not allowed, the solution isn’t removed, and there is no warning.