There's a difference between checking how many things there are in order to display things differently and actually calculating how many things there are based on some a priori knowledge of the schema.  It's a matter of coupling, in that doing that maths (be it actual addition or set theory or whatever) couples the view to the backend implementation.

As you say, the Organisation model (or some other tiny utility class) might be a better place even than a helper, as with helpers there's a risk of just brushing the coupling under a rug.

The key point is, the partial shouldn't need to know about `Organisation#govuk_status` and barely needs to know about `Organisation#live?` or `Organisation#exempt?`.  All it needs to know is the number of live organisations and the number of exempt organisations, and it needs to know where to go to get that information.  The rest is up to you.