I hope he has a speedy recovery.
For all of you young folk, when you acquire Medicare you have to go in to your doctor for a annual Medicare checkup. You have to go in because the federal government requires your doctor to measure you. They want to know how fast you are shrinking in height. And the first question you get is have you had a fall in the last year. Your tax dollars at work.
Benefits don’t decrease, you just stop getting additional delayed retirement credit.
Typically your benefits are calculated based on monthly earnings over 35 years (weighted). Assuming that annual income increases occur every year (which it does for the vast majority of people), then delaying retirement after 70 still results in a larger check because more earlier months (early working career) drop off and are replaced with higher income months from following years going from most recent to oldest.
No once check is reduced for filing for Social Security after 70.
NOTE: It make no sense to delay to post 70 unless you are independently wealthy and just decide not to take social security at all - which is an option. But that is a different issue.