My initial hunch the Japanese are truly worried about being left with the soon to be way devalued documents! The Japanese hoped to keep it secrete they are bailing on us!
If the owners of those bonds have owned them for 6 months, AND they are the 30 year bonds...those bonds have dropped in market value by 35% since December 19th when they were yielding 2.52% (now the yield is 4.65%).
So the $134,000,000,000 par value would have become about $88,000,000,000 market value today.
This week the US borrowed about $140,000,000,000 so if someone tried to sell these bonds the market would have crashed.
My foil hat tells me these bonds were headed for a shredder in return for some "in kind" consideration.