I think the Ranking system itself is bit wonky, sometimes it seems to give a lot while other times it gives very little and same with going down in rank. Initially it had very big swings but now it has slown down to crawl. I haven't honestly seen much difference between any of the Silver and Bronze ranks I've faced so far. Sometimes Silver ranks use barely modified Green starter and Beginners use full fledged UW Control.

There are also multiple cases of people with strong decks, the most obvious being people who spent money during early beta or dropped bunch just as it went open. Then there are people who fully went after one spesific deck and probably have most of it aside from maybe some dual lands and maybe few rares. Sometimes its people who have half complete deck but they pull the "right" side of it. Rest might be very strong budget builds that rely mostly on synergies and the few bombs they have.

I think they did mention starter decks being pitted mostly against others that play them though.