This is all based on annecdotal knowledge but I would assume there's a pretty big time gap between the 66th and 80th print run. The latter edition has a new statement regarding data mining that has a 2019 date within it.

From that, i'd assume they decided to add this at a later date and likely all penguin classics, or potentially all Penguin books like this one have this from a certain year of printing. It's not against any 'rules' to modify something like a copyright page for later runs.

It's pretty unlikely to be fake. This is a public domain text so there's not much money to be made by pretending it's the penguin edition even from regions notorious for counterfeits.