Since this is CDMA and not as open a system as say GSM, I'm going to agree with Verizon. You left out what the Verizon SIM is from. They have at least 2 and more variants then you have to get them to activate it on their network by giving them the info they ask for. I defer to the carrier for exact instructions as they change over time but in short, yes.
There's another issue is they may not allow that phone if it's the usual deal where you get the phone for free or cheap and must be on the Spring plan for years to pay off the phone. I will not write at length here as so many entitled want to get the deal and then split from Sprint or another carrier and exclaim they bought the phone along with complaints that the other carrier won't accept the phone due to the IMEI check.
Be aware of deals that are too good.
I know that Oneplus partnered with Sprint for the 5g variant of the 7 Pro but can it be unlocked to work for other carriers. I have Verizon and when I put my sim in the phone, LTE lit up and I could receive and make calls, just not answer them. But when I restart the device, the Sprint logo still shows up and in the device settings, it shows Sprint as the carrier. When I called Verizon, they just said i needed a different sin card. Would this work?