I think you just have to be a bit more flexible in understanding what was intended by "double the amount of information in one character". In fact, as you point out, the shortest translation of あほ would be "fool", which has twice as many characters in English. That's the sense that's intended.
The CJK languages don't use spaces and many words are only 1 or 2 characters long.
(382 characters)
文字に就き情報の二倍と言う事を掴むため、余裕がもっと必要だと思うけど。実は、君の言う通り「あほ」の一番短い英訳が「fool」に成って、長さは日本語より二倍です。そんな解釈が出る。
日中韓は、間隔も無いし、単語の長さとして、１～２字も多いです。
（122字)
Not quite 2:1, but you can see the point.
Biting the hand that feeds IT
