I don't know what the official line here is at all.........but I've always taken these eating guidlines slightly with a pince of salt and used them only as guidelines not as the definitive (- given that ideas and advice tend to change from generation to generation or even year to year).
Personally, my view is - that if it's safe for you to eat it, then it's safe for a child that's over 12 months to eat (as long as they can cope with the food, ie not going to cause a choking hazard etc)
What do the Japanese do? I think the best thing would be to follow their lead here, they're the experts on their foods and ways of living.
Sushi, i have no experience of, but the parma ham kind of things - DD loves these and was, I think, about 2.5 when she first had it. The only thing with this meat is, that it's quite difficult to chew and swallow, it's quite tough for LOs. But might just enjoy the flavour anyway?
Just my twopence worth.