Quite probably there are differences between fields. In biomedical literature reviews the search terms and databases are detailed, and (in systematic reviews) a PRISMA flowchart [0] provided. The theory being that other researchers could repeat the searches and the in/out decisions and get the same stack of papers to review.

[0] https://www.prisma-statement.org/prisma-2020-flow-diagram

Okay yeah that sounds closer to what I'd call a meta-analysis. In linguistics (which is the field I was in) "literature review" just means "someone looked around and read some papers they thought might be related". There's no expectation that it will be systematic in any replicable way.