When a widespread species is split into two or more smaller taxa, it can be very difficult to correct this on iNat. If there are multiple IDs using the old taxonomy on an observation, it may take a half-dozen or more new IDs to fix what should be an easily resolved problem.
As an example, the ubiquitous Humbug Damselfish (Dascyllus aruanus) was split so that all Indian Ocean specimens are now D. abudafur. (This change actually took place in 2014, but nobody on iNat noticed until now). Unless I am mistaken, there is no easy way to update these observations. There certainly should be.