Mr. Fan's explanation earlier.
It's true that multiple I485's can add more workload at the very beginning. But USCIS will find out very soon that there has been a prior I485 for a person, and will update it instead of keeping multiple I485's for one person.
If anybody has got multple A#'s for their multiple I485's, then I would say that Mr. Fan's explanation could to some extend be right.