Yeah, this map shows something slightly different (and possibly more interesting) than population density/grouping. Really it kind of shows which counties should be split up.
Compare the Houston and Dallas metro areas - Houston has a very distinct large bubble, while Dallas has more overlapping smaller bubbles which make it look smaller, even though it contains more people.
Usually you want to divide your visualization field by some other field. In this case, you might want to do (population / area). For other sorts of things like visualizing a particular demographic, you would often want to divide by population.
I don't think the article solved the mystery as the Chinese are not at all unfamiliar with the Latin alphabet.
Chinese students learn the Latin alphabet and use them to spell words before learning Chinese characters. Chinese keyboards only consist of Latin characters. To enter a Chinese character, you type its pronunciation and then select the desired character from a on-screen menu.
"To enter a Chinese character, you type its pronunciation and then select the desired character from a on-screen menu."
Not everyone uses a phonetic typing method. Many people use wubi (五笔) which is based on the structure of the characters. Although this still uses a QWERTY keyboard, I suspect it doesn't help make people more familiar with the roman letters (in terms of memory, or mapping letters to English sounds).
The east coast has a much higher density of small counties, giving the NY area a look very different from that around LA.