and pardon my poor education in the world of financial system.... I have not heard this kind of economy before where the rule of the PDC can be reverese any time.

First, let us scrutinize keenly. What are PDCs for? for security purposes and for payment in the future of an account - accrued or non accrued or for the consumed transactions

What about if the PDC is payment for an accrued account which will only be materialized in the future? Imagine the scenario, the seller/vendor has already cashed in and taken your money prior to the consumation of the trading?

In which ever angle you look at it, PDC is for future payments. What are PDCs for if these are encashable anytime?