@aaugustin thought I dismissed your idea a bit hastily, so I gave it another thought. The problem with `@queryset_only` is that we'll need the opposite decorator for the opt-in mechanism. Or it could take a boolean argument `@queryset_only(False)` but IMO a real boolean attribute is more explicit. Also I think we can easily add it later shall people want it since it's just syntactic sugar around a method attribute anyway. Finally I'd like to stress how uncommon it should be, there are very few public `QuerySet` methods that don't make sense at the `Manager` level: out of 36 methods that we've removed from `Manager`, we only use this twice and that's for the base implementation. That said, if more people feel strongly about this, I'll add it.