Why the inconsistent API?

gistfile1.rb

class Company < ActiveRecord::Base
  has_many :employees
end

class Employee < ActiveRecord::Base
  has_one :position
  belongs_to :company
end

class Position < ActiveRecord::Base
  belongs_to :employee
end

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# time to build mulit-model form

company.employees.build
employee.build_position

# why the inconsistent API???