Throughout history, Go has been linked with gambling, particularly gambling by comparing captured stones or winning margins. So it stands to reason players had been very sensitive to the margin of winning even if they knew they had won the game. It is not just enough to win but a bonus to win by a larger margin. After thousands of years, it stands to reason players had been keeping scores and have quite a good sense of the margin the first player was expected to get (先手利), and how to minimize it if playing the second. There is a reason why we have records dating at least to the 19th-century imploying komi (played in 1853, 5 points komi, and likely not the first).
However, ranking players using the dan system is a different matter. And for the longest time, it is more related to the guild-like structure of the Great House. Where establishing seniority and competing for authority was the main goal. They were not trying to make it fair but understood players naturally have different strength. Sometimes rank is not even linked to the teaiwari between players. A player can have different teai with different players, and only when one has beaten enough of the stronger players and changed all the teai through a series of games before their “official rank” can be recognized (and sometimes even if they were strong and beaten others, they still didn’t get the promotion, due to politics in the Great houses).
BTW, I’ve been weighing on how much context do I have to bring up. Since literally this was a research in the Taiwanese amateur communities first, and I have way more materials related to it than others. However, other contexts in mainland Japan at the time matter a lot for the subject of this particular komi system, since it originated there in a slightly different form, and it would require some background beliefs I talked a bit here - how they view the teaiwari at the time. It matters a lot why they choose certain komi values. I’ll try to concentrate on just one subject in one replay to make it easier to digest, and less taxing for me drafting. Less relevant subjects like the activities of the amateur communities in Taiwan or in mainland Japan in the early 20th century I can save for another post.