Jeez... maybe, again, Fremont was out of *this* part (the cover). Lol.... And, yeah, I see that in the manual, which isn't exactly 'current', it's from January (the PDF version).
The covers I’ve seen in person with tow packages look like the first photos at these sites:
How to install the Tesla Model X tow hitch receiver
Installing the Hidden Trailer Hitch - 2016 Tesla Model X Long-Term Road Test
Note, however, that my own experience has been on older Model Xs (90Ds), not current production, and the plastic trim around it is different too, so maybe there is a new cover.