I think you’re talking about his column from Tuesday [1], which talks about different research at the Fed [2] that suggested that there is a trade off between “credit provision” (i.e. private lenders taking a risk and extending credit to their customers who they have relationships with) and “stability”. In a credit crunch, investors could flee to a CBDC and make the crisis worse.

[1] “The Fed vs. Stablecoins” https://www.bloomberg.com/opinion/articles/2022-02-01/hedge-...

[2] “Stablecoins: Growth Potential and Impact on Banking” https://www.federalreserve.gov/econres/ifdp/stablecoins-grow...