Just because it is expressed in YAML doesn't make YAML the party to blame here. I would say one of the main concerns I have with anything in GitHub Actions related to the word "merge" has to do with identifying the last commit for a merge, not merging of objects in YAML.

If you have two workflows... one to handle a PR creation/update and another to address the merge operation, it is like pulling teeth to get the final commit properly identified so you can grab any uploaded artifacts from the PR workflow.