The fact is that because he crosslinked each site to the other steemit will most probably never be recognized as the original for this particular article. This particular page is recognized as duplicated content, and google's algorithm doesn't care if it's from the same author. It's bad from a seo perspective regardless of how you see it.

We can either toss a coin and pray google indexes an article on steemit first, or just ask people to post here first with 3-4 hours difference. I don't see any benefit for the author by posting simultaneously on multiple platforms. His reach will be pretty much the same. But there is benefit for steemit, because these 3-4 hours will rank it first as original, as the "relative popularity/traffic " won't matter at all. The thing is medium is probably crawled more often (due to relative popularity/traffic as you mentioned). And I think it's fair for people to post their stuff on steemit first. I doubt this post would get in any other platform (medium, hubpages, or even a self published site with adsense or other monetization) 50 $ :)