Think you are misunderstanding @a0x1's point. Seems they are touching on the point of people using a witness auto revoter and there beinh another metric, presumably involving other account activity such as post voting, to determine if the account is active.
Think the premise is that a witness revote for an otherwise inactive account should not count.
Yes, an auto voter could be created for witness votes too. Ultimately, bots can carry out any activity on here, so I'm not sure there is a foolproof way to code these kinds of features, but they will have some effect in important cases, such as where users literally physically die (and don't set an auto voter).