I think the key is that, they feel they need to provide more information, in order to appeal to the Japanese customers. Non-Japanese (be it European, Asian, or American) businesses will often do this when they do business in Japan.
Let's use an example: A potential pax is looking at your website for full-flat seats. Instead of relying on cool-sounding ad copy, you show him every little detail on the seat. Show him how far the recline goes, how the headrest extends, how the PTV menu operates, how much space there is when every pax goes full flat. He sees all this and thinks "woof, I know the ins and outs, there are a couple small things that I mind, and I found the answer on this site" and thinks more favorably of your airline.
This as a marketing tool seems to be more powerful in Japan than elsewhere.
Back in 1993 I chose to learn Japanese, because I was a car guy at the time, and I couldn't find vital engineering information in English-language automotive publications. They're often all over in Japanese publications.