This county used in iNat is outdated. GADM has it wrong. It used to be a unified single county, but was split into 2 separate ones way back in 2000.
They are now the separate counties of Haldimand and Norfolk.
A proper shape file for Norfolk can be found here : http://opendata.norfolkcounty.ca/datasets/county-boundary
One for Haldimand is here :
https://haldimand.maps.arcgis.com/apps/webappviewer/index.html?id=af86138edf214cc291a2d8db5aebec9c
I know as a curator I could do this, but am hesitant to unilaterally do something that will cause an update against almost 40,000 records.
Also would have flagged on the site should such a facility exist to flag places.