This was previously covered on the forum, I will try and find the response and link to it, but a GBIF employee themselves confirmed that if an iNat observation is deleted they remove it there.
If its identity is changed, they receive and apply that change to their record. If the change results in it returning to needs ID status, it will be removed from GBIF. If it is then again further corrected and returned to research grade, it will go back into the GBIF records
EDIT - here is the reply confirming this written by a GBIF staffer https://forum.inaturalist.org/t/observations-of-cultivated-plants-on-gbif/5296/4