Not really. I did quit a lot of testing on this awhile back. I’m not suggesting the guy is or is not doing that, but having a low CR relative to your MMR can help you push up.
I talked about it some time back.
You can keep dropping down and potentially gain ‘momentum’ on your push back up. The higher your MMR is relative to your CR, your CR basically gets shielded while your MMR stays the same if you leave a match.
It’s really not. 
Legitimately not trying to be obtuse or argumentative. 100% saying this because I think it’s a problem and players can exploit it. Not for massive gains, but gains nevertheless.
I noticed it when I was climbing to 2.4 the first time.
Basically you drop back and you can quickly ‘sling shot’ back up and often times hit past where your original high was. Granted, it still means you need to win those games, but again, it’s about building that forward momentum. You could do this a few times, eventually get some ‘lucky’ queues and shoot well past what you might have gotten had you not taken the losses.
Beyond MMR inflation, it’s why making a fresh alt can actually be an easy way to shoot past your main. You get so many successive wins in a row that you can even get rating for a 1-5 match. Kinda silly.