Fed's Williams Says It's Still Early Days On Questions Involving Stablecoins; Stablecoins Are More About Payments As Opposed To Stores Of Value; Is Less Worried Than Some About Risks Created By Stablecoins; Doesn't See Rising Financial Stability Risks From Stablecoins; Doesn't Know Yet How Stablecoins Will Impact Demand For Reserves; Fed's Ample Reserves System Is Designed To Be Flexible, Can Respond To Stablecoin Impact