Dapeng

One rikishi's non-historical win becomes a historical loss of another rikishi ...

There are also other requirements such as "outstanding strength". Losing 4 bouts in one basho can't be considered "outstanding".

It seems no one who had regularly yushoed had ever failed to reach yokozuna position and only yokozuna was seen to alternate between yusho and non-yusho.

I don't think a 11-4-Y will lead to promotion but a 13-2-D or -J will. It depends on how he manages the pressure.

I think Hoshoryu was promoted because of his impressive performance on day-15. Still, some people considered his 12-3 yusho being "monotarinayi" (not good enough).

A 12-3 yusho next basho will probably not enough for Onosato to be promoted, but a 13-2 yusho will.

Would be interesting to see. Anyway, we've saw once-in-a hundred years yusho.

I think it's possible to have only one ozeki and no yokozuna. For example if Hoshoryu retires (although unlikely) and Kotozakura gets demoted after this coming spring basho?

Had M19 ever appeared?

It's said that when Asashoryu saw Hoshoryu beaten by Kotozakura on the last day of last year's Nov. basho, he said that the Mongolian-born rikishies' dominance of sumo that he started was effectively ended. Now we can say that the Mongolian dominance will be continued for a few more years, at least.

Sure, 13-2 is a yusho score these days. In recent 3 years, more than half of the yushos were 12-3 or worse. On average, almost 2 wins less than the 20-years' long Asa-Haku era. Look at Terunofuji's 10 yushos: 5 were 12-3. On the other hand, Hakuho only had 1 yusho of 12-3, out of his 45 career yushos.

Of the 19 yushos from 2022, 11 were 12-3 or worse, but of the 17 yushos from 2019 to 2021, only 4 were 12-3 or worse, and from 2010 to 2018, for 9 years, only 4 yushos were 12-3 or worse ! Clearly, Hoshoryu would have had no chance to be promoted to yokozuna before 2019, but quite deserves it these days.

"優勝に準ずる成績" is either a "yusho-dotten" (playoff loss), or a score (eg. 14-1 in Hakuho's days or 13-2 these days) that is in most cases would be a yusho score.

For Koto it's quite clear. Unless someone get a 15-0, NSK will promote Koto even with a non-yusho13-2. For Hosho, a 13+ yusho is required.

As mentioned in a previous post, a tsuna-run had a successful rate of 20% (9/44). Koto should also have about 20% of chance in January. Since YDC had affirmed Hosho is on a run in January, he is also supposed to have 20% of chance but I think his chance is smaller than Koto, say 15%. Thus the possibility of a double promotion in January is quite low, only about 3%.