Let's take a single person who has an annual benefit of $16,000 starting at 62, or $28,000 starting at 70. Assume he/she also has a portfolio of $450,000.
$450K is not enough money to FIRE. That's not enough to be considered Financially Independent. I think the minimum threshold is more like $1M -- or more.
This person could
A) Start at 62, take a 4% SWR form the portfolio for $18,000 and have $34,000 of spending money.
B) Carve $225,000 out of his portfolio to provide 8 years of withdrawals at $28,000 each year*. Take a 4% SWR from the remaining portfolio of $225,000, or $9,000 per year.
If they chose B, they need to spend some time with a good book on asset allocation. Instead of a 60/40 portfolio, they have a 30/20/50 (50% cash). That's just a fancy way of implementing a "spend all my own money now and depend on SS to save my bacon when I turn 70."
NTTAWWT. Everybody gets to make their own decision.
Personally, I prefer the Financially Independent aspect of FIRE. And if you are depending on SS, then be definition you are not F.I.
Arguably, if you are depending on a pension or annuity you are not FI, either. But the difference is that a pension or annuity is a contractual obligation. Social Security is not; the government can change SS at will, and you have no recourse.
As Darth Vader said, "I am altering the deal. Pray I don't alter it any further."
When we retired we moved into a community of mostly retirees.
A couple of years after we moved in my wife went to a neighborhood women's coffee, about 12-15 ladies. During the chatting, one lady mentioned that if either she or Jim died, and their SS stopped, the other would have to sell the house and move in with the kids, because the loss of that SS would not leave the survivor with enough income.
DW said what happened next was interesting. There was a group of wifes who nodded and said, Yes, us too. There was another group who looked at each other, gave a little shrug, did not nod, and remained silent.
If you retire on the cusp of being FI, you have to plan carefully so that you don't wind up in that first group.
If you are soundly FI, then you will be in that second group, and you don't have to bother trying to optimize what you get from SS. If worse comes to worse, you just shrug and wait an extra year before trading in the BMW for a new one.