Obviously, when you copy data across to another platform, errors will occur. Sometimes it is me, sometimes it is in the data. I have only indicated when a governor was in office and predecessors and successors.
The data is provided in a way that makes it easy to query; no information on elections (many governors were not elected) but proper start and end dates. The dates are as provided on the Wikipedia lists, articles for a governor are often more precise. People from Nigeria often are known by different names, I did add labels where I needed them for my disambiguation.
When you want to know how many of these fine gentlemen are still alive, it will take some effort to kill of those who are still walking around according to Wikidata. It is relevant to know if a governor was elected or not. To do that properly you want to include election data elsewhere; there is no one on one relation between a position, elected officials and them being in office.
There is plenty to improve on the data. When people do, Listeria lists will update. Maybe someone will consider updating the English Wikipedia lists.