I have seen no evidence of this, and it has been a problem for years. At least the forums largely believe that there is a serious deranking problem now, largely thanks to BTC constantly posting videos on the topic I believe.
However, forum opinion isn’t really relevant. It’s the devs that, well, develop the game and they are showing no signs of addressing the problem.
They said they were rolling out anti-throwing measures with role queue, but whatever mechanism that is, it’s either fully in force or over and done with. It probably specifically compared pre- and post-role queue MMR and is no longer relevant, but they weren’t entirely clear.
Of course, Jeff Kaplan did answer a question about free duplicate console accounts and they he said they have some ideas about that, that they might work on after OW2. Which would be nice for console players, but wouldn’t solve the problem completely … account farmers would just buy new copies the same as they do on PC, but at least it wouldn’t be a free for all. It wouldn’t help PC at all.
If they have any plans to address deranking in a more general sense, they haven’t shared them with the playerbase. Given how long the game has been out and they haven’t addressed the problem yet, I suspect they aren’t going to. Ever.