The user stated they did not activate with a Verizon Sim before trying the t-mobile sim. Another user confirmed they had a similar issue only on their iUP that they ordered online, their in store version was unlocked even after activating with Verizon.

Apple's order page also clearly says all the version are unlocked except ATT Next. Apple apparently failed to update their site regarding the Verizon issue. That is Apple's fault, not the person.