snapshots not getting created with -u nor tagged for cleaning up

I have code that does
```go
	expect.FromSnapshot(t, t.Name() + "Snapshots",
		comparabletypes.NewJSONFromString(somString))
```
where t is a sub-test (that is, this is running inside an outer `t.Run`)
and when running with `-u` this snapshot does not get created, and when one of these snapshots exists but isn't used it isn't fagged by Cleanup.
