I've seen this pop up every once in a while since 2015, and I think it is cool every time. Makes me use my cast iron skillet more.
I suppose the study doesn't say just how well seasoned the skillets were. But pretty much every study dealing with cast iron agrees that it contributes some to the diet, in varying amounts.
There is some debate on whether or not the additional iron is helpful, and in what ways, but that it does add iron to the diet is reasonably well documented.