During my Army service, there was a fellow in my office that was from some borough of NYC.
He had such a strong accent, that when he spoke fast from across the room, none of the rest of us could understand him.
And that really pissed him off. He sounded like he was trying to talk, with mashed potatoes in his mouth.
I have a brother-in-law that hails from a New Jersey suburb of NYC, and he has a predictable strong accent, but we can understand him.
Out here in the "no accent" west, I can discern a few regional quirks. For instance I can sometimes detect a Utah accent, partly because I have had relatives from there. Same for Wyoming.
But like the article suggests, those would be natives. Inbound transfers could be from, anywhere.