It appears that someone is curating taxon names by marking subspecies and varieties that are not on POWO as inactive.
Autonyms on POWO:
“Autonyms are currently only included for plant families that have been peer reviewed and which are also available on the WCSP website https://wcsp.science.kew.org/ as well as some in Asteraceae, Ferns and Fabaceae. We hope to add all autonyms when the geography has been completed.”
So, basically, if autonyms are missing in POWO and the iNaturalist plant dictionary, they should be added on request for any species that has any subspecies or varieties listed. Please do not inactivate them!
Subspecific plant taxa on POWO:
“Both POWO and the WCVP names backbone use the IPNI Life Sciences Identifier (LSID) as their ID’s and therefore only plant names that are also in the International Plant Names Index (IPNI) can be shown. Consequently, not all names in the WCVP database can currently be shown, in particular Old World infraspecific names from before 1971 are largely missing but we are working with IPNI to add the hundreds of thousands of missing names”.
It is therefore utterly wrong to inactivate any subspecific names in the iNaturalist dictionary, on the basis that they are not on POWO. POWO cannot be used as the botanical authority below the species rank.
In the case of southern Africa, we defer to BODATSA (http://newposa.sanbi.org/sanbi/Explore) - what other regions default to, if any, I have no idea.
Please - no matter how well meaning - do not inactivate subspecific taxa on iNaturalist without first consulting with the local users and taxonomists.
((see https://forum.inaturalist.org/t/problems-with-taxon-inactivation/24429 - but that deals with issues around inactivation, not the reasons for why inactivation should not be automatically assumed for plants below species rank))