I read that article when it came out. It's a little hand-wavy on the details.

It's good idea to use arxiv because they enforce submission standards. For-profit journals can't do that and society presses try but are not always successful. What happens if arxiv decides it needs to charge for submissions to defray operational costs? It's too early to tell.

They also do not prohibit individual journals from charging for publishing a paper. Not different from today's open access policies.

Bottom line -- for me its not different. It's just someone saying, "I think I can do it cheaper this way."