One redditor decided to put it to the test. He made a guest account, threw his placement matches, and then proceeded to play games just macro'ing to near max army of strictly stalkers then a-moving to victory.
Original Post with replays
Follow Up to outline when he started losing games
I figured it was worth reposting this over here as I see a lot of the same conversations going on in the [L] strategy threads here (I'm only a platinum myself) and it's nice to see an attempt at some actual evidence behind an argument.
I might quibble that this is a pretty expansive definition of macro (he is doing a number of basic mechanical things at a much higher level that his opponents), but it's a pretty interesting experiment and he's obviously not using any unit composition or micro tricks.