There is perfection and there are perfections to process. Over time people learn and develop techniques through trial and error. Think about sushi, it is no more than a few hundred years old, or at least we think so.
I doubt it myself given that Japanese experimented with vinegar and rice since a long time. The development of vinegar, it is a by-product of rice, and so Japanese had to have taken the basic three ingredients, rice, fish and vinegar and tested it over time.
My guess is, the Japanese house wife experimented and fermented fish, and over time, a shorter period of fermentation was tested. The fishermen’s house wife developed her own version of sushi long before it was introduced as a street food in the Edo period.
In fact fishermen would have eaten fish and rice and at the same time would have developed a version using nori, fish and rice under the influence of sugar and vinegar made it more sticky, hence a sandwich was created.