Do you mean “Why do they add...”? It is to distinguish that version from the RWD version. The badge style is the same as the S/X badging. Looks fine to me. The badge can easily be removed if you want a Dual Motor 3.
If your question is, at what point in the production process is the badge added, I don’t know, but likely near the end of the final assembly line. I do not know if you can specify that your Dual Motor 3 be “de-badged”, but I believe some S/X buyers have been able to do that, or maybe the badging is removed at the Delivery Center if requested.
Fortunately for you, you can configure a 3 with the standard black interior at no extra charge. So no need to complain. Aesthetics are a personal preference.