“A person in one of these programs is not able to purchase supplemental insurance or pay out-of-pocket for a better grade of care. “
I don’t understand your comment regarding the VA. Just because a person is a veteran, he is not forced to use the VA.
You can use the VA for service-connected if you want to, and go someplace else for other medical care. You can have other insurance and not go to the VA at all. You can pay out-of-pocket for better care somewhere else.
The same is true of Medicaid- even if you are a beneficiary, you can pay out of pocket for whatever type of care you want.
But, you cannot get Medicaid or VA reimbursement while paying more than the predetermined copay out of pocket (cannot pay for a higher grade of care), nor can there be multiple payers (supplemental insurance).