What does "NOS-production: no" mean?

I recently bought a refurbished unlocked Pixel 3 XL to replace my aging, cracked, broken one of the same model. It came with the bootloader unlocked so I decided to lock it because I didn't like the warning message every time it booted and noticed that in the Fastboot menu of the bootloader it shows: Secure boot: PRODUCTION NOS-production: no I'm concerned about that NOS-production setting; has this device been tampered with? My old Pixel 3 XL shows yes there as well as all other screenshots I see of the bootloader on other P3XL's - they all say yes instead of no. I used flash.android.com and completely flashed the phone to the latest April Android 11 firmware but it still shows no. I can't find any documentation of what that could mean. Any insight would be appreciated!