I found the lack of any horizontal line separating rows in the given examples of good tables off-putting. In the examples given from The Economist they are using horizontal lines and I agree those are great examples.
In most cases they are using dotted horizontal line which is better than a solid line.
In Google Slides or Excel it's easy to use low-contrast shading between dark and light backgrounds which is another less-intrusive way to delineate rows without using a solid line.
This is an annoying trend; it's true that row lines add a lot of noise that distracts from the content, but you should use color and value to reduce the dominance of the table lines, not remove them altogether.
For a small 3 column table, it is not necessary. The tables on the page "Example Tables I" could have done without horizontal lines and a little more space between rows would have been enough.
Hmmm...I had the opposite reaction. "Good guidelines, why don't their Economist examples follow them?" I find very light shading to be way better than horizontal lines.
