Which upon careful examination will show that the key switch is not wired into the Alternator
output , such that turning it off will cut the output circuit. This diagram is pretty standard , you can see the battery
is permanently connected to the alternator
output via the series amp meter.
As I've said I have never seen the key switch switching the output of an alternator. It doesnt make sense. These key switches are typically relatively low current
( 5-15 A) devices and totally unsuited to carrying even small alternator outputs