Schema.org RentalCarReservation extra/missing field

Hello Schema.org,
In RentalCarReservation - schema.org , the JSON example contains "reservationFor.operatingCompany".  However, this field is not under https://schema.org/Car.
Let's not use this field because "RentalCarReservation.provider" may already provide all the organization details of the rental company. 
Any thoughts on the "operatingCompany" field?
Thank you,
-Jimmy