That's ignoring Vernier Acuity, which is a very important effect on displays where the pixels form parallel lines, i.e. pretty much every modern electronic display. It gets down to 0.13 arc minutes, which is why there are several replies pointing out that your theory doesn't match reality, even for people with worse than average vision.
And this figure of 2190dpi? That's 3 significant figures, computed from something that was given to only one significant figure (0.4 arc minutes). You can't do that, and it should be a huge red flag that the source article should not be taken seriously.