That chart should really be zoomed to about 1/5 its size... it goes up to 150 inch? Who has displays that big?
The X axis should go from 10 to 60, the Y axis should go from 1ft to 30ft, max.
As it is, it's not all that useful for figuring out what the density limits of a desktop monitor are. (Average desktop monitor sizes occupy maybe 1/12 of the X axis!)
Well with a 4K display your able to sit closer to larger ones because you will not detect the pixels as easier. I know many people think you want more distance with a larger set, but with 4Ks they are just fine, as long as don't move your eyes to much to see the entire screen.
I'm not entirely sure I follow why you feel this is significant. At least in the US, we tend to measure viewing distance in feet and diagonal screen size in inches, and those are both measures of length. It's not like the two axes are "feet" and "fluid ounces."
Even if it was fluid ounces, that's still not a problem - A line chart of my account balance would have Euros on the y-axis and months on the x-axis. It's still a meaningful chart though...