I believe that this is related to some previous discussions and an open Feature Request (full disclosure, it’s one of mine):
https://forum.inaturalist.org/t/suggestions-for-synonyms-override-options-with-the-name-typed/7978
https://forum.inaturalist.org/t/prioritize-scientific-name-over-synonym-in-display-order-of-species-search/23191
https://forum.inaturalist.org/t/search-results-not-prioritizing-language/38897
There may be other threads about this. If this is the same issue, we can merge, etc.