That is not at all in conflict with the post. The selection effect is one of the sources of the empirical diseconomies of scale the author mentions.
In my first read, I took that to mean from a process and inputs viewpoint.
But reading it again, I suppose the author could be taking a more consequentialist point of view. They are at least as good (or much better), largely because they don't have to do much.
I suppose that's fair, but also a lot of words in the OP to state a truism :-)