When I first got the SIM-free Max and put in the SIM that was in my iPhone X, Verizon could not identify the phone for several days in the app and online. Yesterday, I checked and Verizon correctly sees I have the XS Max.
I was on the phone with Verizon for three hours, for real, launch day trying to get my phone activated. The support rep said a ton of phones bought from Apple for their network were having the same issue. She claimed after this three hours we were the first on their supprt team to find the solution. Much joy was to he had. She pinged her support channel to let the other reps know. Heh.
Also, I still only have two bars instead of four. As I had with all previous devices. :/