Google’s guidelines are not an action plan
According to Google’s John Mueller, the Search Quality Raters Guidelines are not an action plan or instructions for positioning a website in search results. The content of these guidelines does not correspond unequivocally to the ranking criteria of the Google algorithm.
Source : Search Engine Roundtable
Reliability rate: 
We have some doubts…
Although it is not a collection of technical advice for SEO, this document, well known to professionals, clearly defines the type of pages and content that Google wishes to highlight. Indeed, quality raters rely on these guidelines to help Google verify whether its algorithmic signals produce relevant results.
The article “Goossips SEO: Search Quality Raters Guidelines” was published on the site Abundance.