I don't see that as a particularly compelling explanation. OB was not just EY & RH. There were a number of other contributors, on a weekly basis even there would be non-EY/RH posts. Just look at the long list of contributors prominent in the sidebar.

If the explanation is why people will only post comments and not articles because they don't want to take too much of what is offered, then what greater item is on offer in LW that people 'settle' for merely submitting articles & comments?