Why does this library call Sink.Close() during Snapshotting?

[otoolep]

This library closes a Sink to which a snapshot is written, after the snapshot has been written to the Sink:

https://github.com/hashicorp/raft/blob/v1.7.1/snapshot.go#L197

Yet the Godocs imply that the FSM should call Close:

https://pkg.go.dev/github.com/hashicorp/raft@v1.7.1#FSMSnapshot

type FSMSnapshot interface {
	// Persist should dump all necessary state to the WriteCloser 'sink',
	// and call sink.Close() when finished or call sink.Cancel() on error.
	Persist(sink SnapshotSink)

	// Release is invoked when we are finished with the snapshot.
	Release()
}

Granted, it's easy enough to code a Sink to make close idempotent, but is this simply a bug?

[otoolep]

Same question for Cancel() too.

[otoolep]

(Made some corrections to text of report)