Threads fail. Threads are generally the most likely thing to fail in any given mechanism. Generally, when the threads are expected to do more work than just sit there and not move, as in fastening a hinge for example, we try to make sure the threads are all the same kind of material.
I would never expect plastic threads to hold up to repeated use with an iron bolt inside. Something is going to give up, and it’s going to be the soft plastic threads, every single time.
Think about cheap as fuck IKEA furniture, any time they have a bolt to screw in, you install an insert first. We do the same thing in plastic, aluminum, shit even steel sometimes if we want the bolt to fail first.