That link begins with information which conflicts with my observations. I was able to unlock the bootloader without enabling "OEM unlock" from developer settings. I was able to do flashing from fastboot and flashed stock images multiple time. At one time, I tried to check about FRP and noticed that after a reset, Android required me to verify the ownership at *supposed* first boot. --- All of this info is in consonance with the Android Police article linked in your answer.
Now, the XDA article I linked says that OEM unlock must be enabled to have the bootloader unlock but that's contradict…