Buffett owns insurance companies which hold pension funds. They know about fixed-income investments better than anyone. The Fed had told the pension funds long ago to get out of bonds and into stocks and other assets. The average public pension fund now has only 24% invested in fixed income. If the Fed wanted to let fixed income yields rise, they're getting very close to where their exposure to higher interest rates is as low as it's going to get. They hold bonds to maturity for the most part.
https://www.nasra.org/investment