The vital missing detail is the Android SPL at the time you unlocked the phone in order to install /e/OS.
You will be aware from the above that the index on your phone “remembers” the SPL in its last locked state.
No good in hindsight but if you had any evidence of the “locked in SPL” there would be no guesswork. If however you guess that say the next /e/OS build released about now today is ahead of locked in SPL you might decide to lock it after that update.
- Locking the phone will delete all data
The commands to lock the bootloader are at the foot of the install page first link in Post #10 .