Actually when the iPad 4 first came out, you are correct they had the A6 chip. However as I recently found out when I had my iPad at the Mac store the ipad4s that were distributed in late July of that year, had mistakenly been fitted with the new A7 chip. Apple tried to retrieve all of them as soon as they found out however, some fell through the cracks. Mine apparently being one. You should have seen the techs eyes when he saw it. Apple removed all the 4s from the shelves when the air was released and decided to just keep the 2 out as it was such a huge gap between it and the air
I know Apple technicians and I have literally never heard of this happening, ever, and it seems so strange that a company like Apple would unwittingly put a future chip in a current device. A Google search yielded nothing. Do you have any proof? I feel like your technician had no clue what was going on.
As far as I know, every single iPad 4 out there – I owned one – has an A6X chip. When the iPad Air came out, it was briefly being sold alongside the iPad 2, and then among complaints that the iPad 2 was overpriced and too old, Apple replaced it in the lineup with the iPad 4 and sold it alongside the iPad Air. Still an A6X. iPad Air was the one with A7.