Correct, the rule of thumb is “if the install instructions do not mention to lock Bootloader do not attempt it”.
There have been reports on the forum that e-Recovery fails for certain builds [2] – at Gitlab: [1].
I think it is worth noting your experience in the build-feedback threads:
[1] I find one Gitlab backlog issue for beyond1lte
This sounds close (??) to your issue. You might comment there.
I think it is worth recording your exact build_version_string and please can you check the version which currently displays when booted into e-Recovery, perhaps an image just in case anything else is revealed.
[2] A fix is proposed here Feedback for v2.8 - #4 by WillemR