That's probably a more refined way to think about it, but I do want to nitpick a little bit as the quote doesn't say tyranny, just power.
So yes, a group like children with leukemia doesn't hold power in themselves, they do hold power indirectly because of those societal norms. That doesn't mean them holding that power is inherently bad, nor that they'd abuse that power, it just means that certain privileges of power have been granted to them because of circumstance.
Additionally they can just as easily abuse that power by being awful people and using that negative attribute as a crutch. A good example was some dude I knew who was diagnosed autistic and would act like an asshole and then use his autism as an excuse, and sure he's awarded some level of leeway due to his inability to process certain things, but at some point people did have to acknowledge the continued repetition of negative behavior was no longer just the result of his autism. In the same sense a kid with leukemia could go out there, be a dick, and use their leukemia as a shield to some degree because they have been granted some level of power indirectly.
It's a bit abstract, but think of it this way, if I have a hired goon and I say I won't do anything to you but the goon would, it doesn't mean I have the power to physically hurt you myself but neither do I really need to if the goon can. You can argue that's different because I hired this goon to hurt you, but the response is that there's nothing wrong with hiring a bodyguard as it doesn't give me power against it, just protection, and I feel threatened by your noncompliance. Extreme and reductionist example but power is power regardless of source.
So I guess that's what it comes down to, the following when it comes to kid's with leukemia:
A.) If they behave in a reprehensible way you can criticize them for their reprehensible behavior.
B.) Or you can't and they have the power to behave in ways others can't without criticism. It might not be extraordinary power but it's still some degree of power.