You should never assume that a checklist is accurate or complete, but along with atlases (which bring their own set of issues) they remain the only way to document the presence of a species in a location where there are currently no iNat records.
Speaking as someone who added the distribution data for the over 50,000 species in the taxa group I curate into the relevant national checklists (I cant even imagine doing it for subnational levels), they are extremely time consuming to update. It is easier if you have a list that is geographically oriented, but doing for an individual species that needs to be added into multiple checklists - that is very slow work. Somewhere I have an active feature request to try and make it easier, but it got little traction, and I would have to find it.
edit here is the original requesr which generated a grand total of 1 votes
https://forum.inaturalist.org/t/improve-functionality-of-status-tab-on-taxon-page/3517
And what it was merged into
https://forum.inaturalist.org/t/improve-community-curation-tools-for-introduced-native-status/720/2