US losing status as triple-A credit? Is there a risk free rate?

Story on Bloomberg the yields on comparable Treasuries are higher than for Buffet and some other high credits. I received this story from at least two other sources so it is making the rounds and is causing many to ask why. The simple or obvious reason is that the risk on Treasuries is higher. However, given supply and technicals you can get these types of price distortions albeit not often so you cannot jump to the conclusion that risk is the main reason.

Nevertheless, there is the growing view by both traders and investors that there is something different going on with the world's risk free rate. In fact, can we really say that there is a risk free rte when the debt of the US is exploding? The perception is that the supply of Treasuries will exceed demand relative to the supply and demand for some corporates. You can call this a truism but the need to hold Federal debt may be declining relative to what the Treasury wants to issue.