It is not 'largely the same as OTA' on phones with downgrade protection. Once you lock the device again, it's game over because the bootloader refuses to boot an older version of the OS, and you cannot unlock the phone anymore. Happens all the time in the /e/OS and Fairphone forums.

It really depends on the device. E.g. Pixel is quite hard to brick. Though they do sometimes increment the anti-rollback version:

https://developers.google.com/android/images

In that case you have to be careful to not flash an older version to both slots and lock the bootloader, which is possible, because many non-Google/GrapheneOS images are often behind on security updates.