Chuckanut
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
Not yet, correct.
But two points:
1) as the years roll on, with additional COLAs, the time will come when SS by itself will begin to have a nonzero federal income tax due, slowly at first.
2) I suspect that very few people who are living on SS alone were able to wait until age 70 to claim AND had anything close to the maximum benefit. It just doesn't work out that way, for the most part...
IIRC, only about 6% of SS recipients delay SS to 70.