Merge yaml arrays: job tags

There is official doc of gitlab which demonstrates how to merge yaml arrays on example of job script steps Optimize GitLab CI/CD configuration files | GitLab

But when I do same marge for job tags I am getting “tags config should be an array of strings”, no matter what syntax to use ( , -, -“”, [“”, “”] … )

It sounds strange. Is it possible to provide an example of your implementation?