In the UK it's the coroner who makes that descision (unless, e.g. someone dies in hospital and a doctor can see what they died of), and they're independent of the police, so it'd become a multi-agency coverup if they were doing that.

It's the Met, though, so they might just not notice bodies in the first place or be able to add up the numbers they get from the coroner once they get into double figures. For an organisation so institutionally incompetant as the Met, you have to apply Hanlon's Razor by default.