Understanding translations for "nested attributes"

I have a use case where I have an STI with the setup below:

class BudgetLine::Accommodation < BudgetLine
  has_many :budget_line_items
  accepts_nested_attributes_for :budget_line_items
end

In a form for BudgetLine::Accommodation, I have a nested form for BudgetLineItem, where I need the labels for the attributes to be unique for that model; different than e.g. BudgetLine::Transportation etc.

In this part of the Rails Internationalization documentation it states:

"In the event you need to access nested attributes within a given model, you should nest these under model/attribute at the model level of your translation file:

en:
  activerecord:
    attributes:
      user/role:
        admin: "Admin"
        contributor: "Contributor"

I thought this applied to my case, but I can’t get it to work with.

en:
  activerecord:
    attributes:
      budget_line:
          accommodation/budget_line_item:
            unit: Room

Can anyone explain to me what exactly is meant here? Is this just another way to structure namespaced models and doesn’t apply to nested attributes for forms?

would it work like this?

en:
  activerecord:
    attributes:
      budget_line/accommodation:
        budget_line_item:
          unit: "Room"
      budget_line/transportation:
        budget_line_item:
          unit: "Kilometer"