Take a look at the log for a run of the Deploy to GitHub Pages workflow. Specifically, take a look at the logs for that workflow’s Build Docusaurus job. The “Run threeal/setup-yarn-action@v2.0.0” step will install any dependencies. Once that step finishes, it immediately installs the dependencies again in the “Install dependencies” step.
Take a look at the log for a run of the Deploy to GitHub Pages workflow. Specifically, take a look at the logs for that workflow’s Build Docusaurus job. The “Run threeal/setup-yarn-action@v2.0.0” step will install any dependencies. Once that step finishes, it immediately installs the dependencies again in the “Install dependencies” step.