Wikipedia articles should rely on published secondary sources and, to a lesser extent, on tertiary sources.
In theory, primary sources may also be used. Reliance on primary sources can lead to interpretive clambs, analyses, or synthetic claims, which must be referenced to a specific source that makes the same claim or analysis.
It is not proper to rely on original analysis of the primary-source material by Wikipedia editors.
Because they don’t want primary sources to be interpreted “the wrong way”.
Do you have a link to this guideline? I remember that original research is not allowed, but not a rule against primary sources. 🤔
https://en.wikipedia.org/wiki/Wikipedia:Handling_primary,_secondary_and_tertiary_sources_(proposed_guideline)