Crossposting between the two lists has always been a strong memetic feature of discussion between the two.
Not sure what the term 'orthogonal' means, but the two lists were founded by two different persons for two different purposes. A common subset of individuals subscribed to both, but there are also individuals who only subscribe to one or the other.
I truly enjoy the crossposting, because it produces full-ranging discussion
on a given topic, and often two entirely different perspectives result from
the same question.
One can watch the different perspectives unfold in tandem.
Problem? No, design feature!