There is a chance Tesla snipped it from the loom in a "mid refresh", it has been known to happen. Annoyingly my car was in that 6 month window where Tesla decided to stop fitting dimming wing mirrors, and modified the loom accordingly. Some people have reported the latest cars coming without the USB data connector that was previously taped up (non data USB hub supplied), etc.
You're probably right though in this instance. I would take the presence of the grill as a good indicator that the cable is present and tied up there, and if that's the case there's no reason it can't be retrofitted.