I think that given that people will use ranks like infrahybrid and forms, and maybe even subspecies, at least formerly, for subdivisions of interspecies hybrids; I reckon the observations search needs a way to exclude interspecies hybrids that doesn’t get tripped up by this, so it can be used for the species count/search.
Maybe an hybrid parameter, which if set to no, prevents any observation from showing up if its observation taxon is hybrid or genushybrid, or a descendant of such a taxon? If it’s set to yes, then observations will only show up if they are hybrids, genushybrids, or descendants of such taxa. If any, then everything shows up.