Earlier quoted context omitted.
Don't know about Japanese, but other well-known input schemes for Chinese includes Cangjie ( https://en.wikipedia.org/wiki/Cangjie_input_method ), Zhengma ( https://en.wikipedia.org/wiki/Zhengma_method ), and Wubi ( https://en.wikipedia.org/wiki/Wubi_method ). In fact, all of these non-phonetic input/encoding systems are highly non-intuitive and have a reputation of sharp learning curves, frustration is expected. Thi…
Phonetic systems for Chinese aren't so prolific for non-mandarin speakers. 9 square/Q9 is another popular method. The stroke-based methods aren't so arbitrary - they are based on the way you write.
Indeed, they are not arbitrary.
The very invention of them is meant to create something much more meaningful to the users as alternative to the telegraph code and alike, which is nothing more than a bunch of numbers. But I say "arbitrary", in the sense that the classification and organization of strokes in the system is selected artificially by the designers, not something inherently exists in the language and understood by the speakers, difficulties are overcame once you are familiar to the system. But extensive effort is needed for a new user to master the system.