Did they send you back a Verizon phone? Verizon Pixels have locked bootloaders due to Verizon's own policies. They say they are "unlocked" but they only mean carrier-wise. Source: Owned a Verizon Pixel 1 that I sold due to it having a locked bootloader.

Anecdotally, I purchased a 4a 5g from Google with a dead headphone jack. My replacement also had an unlocked bootloader though I think it was also new.