The 3.9% you get from a 6M treasury is annualized (so only 1.95% in 6 months), and the 3% for 6 months (from I-bonds) is actually >6% annualized.
So I-bonds will still beat the 6M treasury bond unless the rates on the latter keep going up.
So I-bonds will still beat the 6M treasury bond unless the rates on the latter keep going up.
Thanks for annualizing (or in this case, 6Month-izing) the rates for an actual apples-to-apples comparison.