Absolute BS from them most likely they are clueless as usual, since there wasn’t any issue with S20 Ultra on their 5G network. You will have no issues with US unlocked model and better model to get in every way. Obviously Verizon wants to get their model with all the customization and junk, what else the Verizon tech is going to say if you ask them. Most of the time they don’t have any clue about phones that too unlocked models. N20 Ultra has all the 5G bands including Verizon mm wave and will work perfectly fine on Verizon 5G network.
Samsung tech confirmed that Unlocked Note 20 Ultra will only pull 5G signal on Tmobile and Sprint. Go call Tier Two tech on VZ to confirm. That's why I went to Sammy tech to reconfirm. This was my own inquiry as I am with VZ, for twenty years, and am looking for Unlocked so if I want to leave VZ, I have capability. My Note 9 is VZ and it doesn't even work on Visible! Unlocked is my preference.