@chcw
We understand you are concerned with content detected by Yoast. We can see how this might give you pause. We are happy to take a look! Let’s see what is going on.
1. How to let Yoast SEO calculate the word count properly?
Please note that the Yoast SEO plugin analyzes the default WordPress content areas like the title, URL, and the main content box (WordPress editor). If you are adding your content through the other plugin or theme content boxes or custom editors (as most page builders do), Yoast might not be able to detect it by default.
2. Will Google count in the words in menu item texts, footer links and testimonials when checking if a page is “thin content” or not?
Please note that while our plugin cannot detect all your text blocks and shows an incorrect analysis report, this doesn’t mean that search engines won’t be able to parse them. Our content analysis is to validate the content of your website and doesn’t really affect how search engines crawl and index your site.
If you like, as a workaround, before you add your content, you can do it using the default editor, check for Yoast plugin advice, adjust your text, and then switch to your custom page editor/builder.
We hope that answers your question, but please do let us know if you have any additional questions or if we can be of further assistance; we’re happy to help.