Just spitballing-- you'd see other firms generate their own versions with slightly modified training sets. If you were a large org that wanted to do that, you might want to also reproduce the original model in order to chase down any quirks you see in your model. Then you'd see the weights don't match up.

Or adversarially-- if e.g. "Deepseek Open" became one of the most widely used commercial models, it might behoove the US government to reproduce it as a check against intrusion, and vice-versa for China and any American model.