Compliant POS manage themselves data outside PrestaShop on their own cloud.
They have total control of data alterations and can certify that merchant, modules or others unauthorized changes cannot be done.
It require to have an history of all changes with date and the reason.
So only operations made on POS can be trusted, all operations performed on PrestaShop are excluded because its not possible to certify that PrestaShop or modules sent right data.