ah, I was misreading this exception below as if "tax liability" was the same as "tax due" (and thought since I had a refund that meant I had no tax liability) -- but I've now learned it's not. Thank you.
"Exception. You don’t have to pay estimated tax for 2022 if you were a U.S. citizen or resident alien for all of 2021 and you had no tax liability for the full 12-month 2021 tax year. You had no tax liability for 2021 if your total tax was zero or you didn’t have to file an income tax return."
