It's not an error, though many people now have a misunderstanding of the term "resolution" based on computer display marketing. When you use a given screen size, then you can use pixel dimensions as a proxy for "resolution," in a general comparative sense (though such things as dot size aren't included).
Yes it is an error.
The resolution of an electronic image -- in this case the image contained within the JPEG -- has nothing to do with displaying or printing. It only has to do with the number pixels and total dimension of those pixels.
The McKinnon image contains less pixels than the other image independent of any screen display. That's all one has to do to see that the McKinnon image was NOT the originating image.
What term would you use to describe the number of pixels that should appear per unit distance when the image is rendered at normal size? While the term "resolution" has many uses, I am unaware of any other good term to describe the above measurement. I suppose one could use "pixel density" or "dots per inch", but I've not seen the former term used for that purpose, and the latter term is rather clunky (it would be akin to saying that the miles-per-hour of a car was 55).