Plato lived from 428/427 or 424/423 until 348/347 BC. By 479 BC the Persians had been militarily humiliated and shortly afterwards the Greek Alliance, led by the Athenians, had them so scared that they would never again engage in a sea battle. So, I do not consider it likely that Plato had Persians in mind when he talked about Atlantis. Not that I rule anything out.
You are right of course, Plato referred to the Pillars of Hercules. But that is commonly accepted to be the Gibraltar Straits. It is not uncommon to have conflicting reports in the ancient texts. Pindar was clear, however, more reliable people (like Diodorus who was a historian after all), place the Pillars of Hercules at the Gibraltar Straits. We cannot discard all other references and take Pindar's as granted.