I don’t think this is a bug as the functionality is working as intended. Tags and descriptions are different than observation fields and are treated as such. Users can search observation fields using these instructions:
https://forum.inaturalist.org/t/how-to-use-inaturalists-search-urls-wiki-part-2-of-2/18792
among other ways.
Changing this search functionality would be more of a Feature Request. However, we’re not accepting feature requests for the Explore page currently. There is an open thread for suggestions you can add to here:
https://forum.inaturalist.org/t/ideas-for-a-revamped-explore-observations-search-page/8439