Having been taught never to use a comma before ‘and’ at school, I was under the impression that any comma before ‘and’ was frowned upon. And that the Oxford comma was the breaking of that rule, regardless of whether it’s part of a list or something else. But you may be right. I’ll use one where it improves clarity, less often if it makes no difference. I find some modern work has too few commas, which can make things hard to read sometimes!