In newer versions it's entirely blocked. I've unlocked OnePlus 6 and it was quite easy, because there were no updates for Android 12. On OnePlus 7 it was a different situation I needed to downgrade first to be able to unlock the bootloader. And it only works with vendor tools in a special service mode. These tools are not provided for new phones anymore as far as I know. And I mean, what do you want to downgrade to when Android 12 bootloader stock image is locked.