No it's not. It's just the Post Office trying to save money by being slower. This quote from the article describes it (note the last sentence in particular): "

No it's not. It's just the Post Office trying to save money by being slower. This quote from the article describes it (note the last sentence in particular): "Potential Delays: Because most postmarks are applied at processing facilities, the date inscribed may be later than the date the mail piece was first accepted by the USPS. This discrepancy is expected to become more common due to the implementation of the "Regional Transportation Optimization" (RTO) initiative and the adoption of "leg-based" service standards."