Actually the FFR is for an unsecured loan. The “repo rate”, which is slightly lower, is secured, and that is usually secured by the 91-day, as I understand it.

It certainly doesn’t seem that anyone is liquidating US Treasuries at this point. That’s a big part of the commericial paper problem … too much flight into “cash”, as represented by the safest debt instrument of all, the 91-day US T-Bill.