Are superimposed wiper sold?

From the small markings on the ends of the wiper in my view, results in a production date of 3/2013. I have documented this with photos and the suppliers receive the following information:
"We thank you for the pictures provided to us.
Since all our wipers are supplied directly from Bosch and the storage time never exceeds 10 working days, we can not explain this.
The only logical explanation and would be that the holders of the windscreen wipers have been produced earlier, the wiper blades, however, until much later.
You can install this but reassured.
Should the outcome of wiping but resist not expect in order to be, so we replace them naturally and without delay. "