I agree completely with that.
Either date of service or If billing to the consumer were to be deferred pending insurance processing, then there is no set due date upon which to become delinquent.
The DOFD would then be the date due set in the billing statement, if not paid by that date.
Most hospitals, doctors offices, etc clearly state that you are responsible for the debt, even if waiting for insurance to pay.
You are supposed to pay then be reimbursed by your insurance.