The bootloader being locked doesn't keep you from activating developer mode, any phone can do that, bootloader locked or not. The only phone I've ever had with an unlocked bootloader is the 6p, and every phone I've owned I've activated developer mode.
I would say it has something to do with it being locked in demo mode, so customers can't mess with the settings or possibly screw something up (in Verizon's eyes anyway).
Sorry I wasn't clear, I meant when I tried to activate developer mode, it stopped me from getting there with the demo mode only message. Had I got it to developer mode, I wanted to see if it has an OEM unlocking toggle, like my 6P. I figure until Verizon Pixel 2 units arrive on customer's hands, that toggle (or lack of it) would prove if it allows for bootloader unlocking.