No. To my knowledge, curator status has never removed by staff due to the user’s inactivity. The status may be removed by staff however if someone has grossly violated the policies in Curator Guide or Community Guidelines, or I suppose by request of the curator themselves.
I commented on and resolved the flag that I believe you are referring to. The curator in question was not holding anything up - any curator could have assisted in resolution of the flag. For most species on iNat, any curator can make changes to the taxonomy. But vertebrates, for example, are pretty locked down and can only be edited by a small number of “taxon curators”. You can read more about this at https://www.inaturalist.org/pages/curator+guide
Note: there is a very large backlog of unresolved flags on taxa: https://forum.inaturalist.org/t/big-ol-backlog-of-taxon-flags/4464 Looks like the oldest unresolved taxon flag is from 2013.