I have seen that but I also struggle to buy into it. They have also said win streaks are not a thing anymore, which they did years ago but one or the other has to exist for the story I am about to tell to make sense.
I tell this story a lot because it is relevant to a lot of situations (including here now) but in season 2 of Overwatch I decided to take a break from Tank and DPS to learn Support. I focused largely on learning Zen (but also played Bap Kiriko and Ana as needed) but was stuck for quite awhile in Plat, which is why I always say it is not impossible for someone to be highly ranked at one role and much lower at another. I had about 60 wins bouncing between high and low Plat but I could tell I was improving at every aspect of Zen (and the others to a lesser extent).
Now to the relevant part of the story for this topic. I was at 2-2 in placements but feeling really good as I had popped off in all 4 games and the losses felt very narrow. Suddenly I went 3-0 and went from Plat V to Plat III. Then went 5-0 5-0 and went Plat III-> Plat I-> D4. Then went 5-2 and went from D4 to D2 to finish up my crazy run in D2 (I then hovered for a few cycles improving slightly before jumping to Masters in a similar way).
Now the two things I take away from that are: if you get better then you will climb and it should be impossible to go from P5 to P3 going 5-2. The math simply does not add up and I didn’t think much of it at the time but I was popping off in a huge way. Win streaks have to exist for the latter skill up and skill based probably exists for the former.
Now they have tuned a lot of nobs and made a lot of changes over time so it is hard to tell what has changed and what has not, and also the most dangerous thing in coding: what has changed that you were not intending to. I watched them in an interview talk about how they simplified the matchmaker because they realized it was making things too complicated and they realized they could simplify things (something that every algorithm writer can relate to) but I do wonder if that simplification applied to the gain step as well.