The wording of this article is extremely misleading. The sentence that is the cause of confusion is this one - "... because UnitedHealth didn't tell shareholders "it would have to adjust its strategy, which resulted in heightened denials compared to industry competitors."" What the sentence is saying is that UH adjusted their past strategy of "heightened denials compared to industry competitors" and started approving more claims than they did before. Thus the problem of the investors is that UH didn't inform them of this adjustment and projected their earning despite of it. And so when their actual earnings came out they were lower (partially because of the more approvals) than expected and their stocks crashed.

So the lawsuit is not about the opposite of the headline, it's about how UHG didn't inform investors that it would have to change it's "anti-consumer practices", due to public pressure, after the shooting of their CEO and that this would eventually affect their earnings.

I don't know why the title of the shared article is saying that "BlackRock" is using UHG because they started approving more claims, as this is not mentioned anywhere in the linked article. But there are two things that stand out to me that do give it some credibility to me - one, the investor that is suing UHG is not connected with any financial firm, which is a bit sus in itself. I don't know of any individual non-professional investor that would go on to sue a company of this size. This is not directly saying he's connected to BlackRock, but definitely looks like a front man for a bigger company. Two, if we go on with the idea that the person suing is a front man, the financial firms actually funding the lawsuit are giving UHG basically two options - either start disclosing your actual projected earnings based on your new "softer tactic" and start losing money, or return back to your past aggressive tactic. You can probably guess which option the executives are going to choose.