Mr Ferguson may claim to not have an English accent but he certainly has a British accent since Scotland is part of Britain. It is part of Great Britain and so the Scots speak with one of the many British accents just as a New Yorker or a man from Georgia speak with different variants of American accents.
Maybe you misunderstood the conversation. Maybe he actually said he did not have an English accent. That would make sense.
Let me try to explain it to you this way.
I'm from Texas. Someone from Minnesota is going to sound differently from me.
We don't say we have an American accent. We use our regional accents.
I have a Texas accent.
I didn't misunderstand Ferguson, nor did I misunderstand my daughter's friend.
Maybe you didn't understand my American accent?