The best follow-up we have is from the cruise ship, where at the time of testing more than half of those who tested positive were asymptomatic, but ultimately something like 80% of the confirmed infected ended up with symptoms.
I probably saw that factoid hyped up in multiple media stories which misconstrued the original paper.
If anyone knows of more reliable recent sources about this, it would be great to clear it up.
Also lots of information in the comments.
https://www.medrxiv.org/content/10.1101/2020.03.18.20038125v...
In particular, that CDC report I linked above citing 46.5% is from late March (early release on March 23, published on March 27th).
That report cites a website by the Japanese Ministry of Health, Labour and Welfare [1], which itself confirms that 46.5% (331/712) is up-to-date as of March 26th.
I'm not very knowledgeable about stats, to be perfect honest, but I think your paper must've turned out to be a red herring. Maybe they got unlucky with their sample?
[1] https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/newpage_000...