https://www.irs.gov/newsroom/tax-day-for-individuals-extended-to-may-17-treasury-irs-extend-filing-a...

Read that.

"This relief does not apply to estimated tax payments that are due on April 15, 2021. These payments are still due on April 15."

For retirement, it is for the filing by the filing due date with extensions, so that is a relative deadline.