I don’t know the specifics of who the buyers were.
Again, quoting from the ZH article that posted the story:
Indirects(?) awarded 72.0 (up from 70.8) and above the six auction average of 70.3
And Directs awarded 20.6%, up from 20.3% in September and the highest since April. Dealers were left with just 7.5% of the allotment, the lowest since January 2023.
It makes me very suspicious, just as the 10y was trading at 4.34%- the highest since July- and was set to spike on even a
hint of an ugly auction. Instead, the yield promptly tumbled about 4bps after the auction results were announced, which
in turn sparked a new wave of stock buying, and so on.