I think you missed part of running_man's plan. Did you notice the $180,000?
I'll convert your numbers to annual and do a little rounding because it's easier for me to see what's happening.
You say the choice is:
A. Take SS today.
Starting now, $30,400 from SS + $40,000 from 4% SWR = $70,400 total, indefinitely.
B. Defer SS for four years. Your plan is has two income levels.
First four years, $0 from SS + $40,000 from 4% SWR = $40,000
After that, $40,200 from SS + $40,000 from 4% SWR = $80,200
Given the choice between A and B, you'd take A. I suppose most of us would.
But, rm has a different plan. Again using your numbers:
A. Take SS today.
Starting now, $30,400 from SS + $40,000 from 4% SWR = $70,400 total, indefinitely.
C. Defer SS for four years
Move $160,000 from my $1 million portfolio into short assets (CD's, short TIPS), leaving $840,000 invested in stocks etc.
First four years, $0 from SS + $40,000 from ST + $33,600 from 4% SWR = $73,600 total.
After that, $40,200 from SS + $0 from ST + $33,600 from 4% SWR = $73,800 total
Notice that Plan C allows me to spend more money in the first four years, and spend more money in the remaining years then Plan A. I prefer Plan C over both Plan A and Plan B. (Note that if I'm a more conservative 3% SWR person, the advantage of C is even larger.)
In fact, that's what we did. When I retired, we had a laddered portfolio of CDs and I-Bonds that was designed to fill the gap between retirement date and SS start date. We've mostly spent that portfolio down.
Modified Plan C. As the SSA has been mentioning for years, benefits are reduced by 25% starting in 2033 (perhaps earlier) due to the trust fund running out and general economic malaise. Then, payments become $30,150 from SS + $33,600 from the reduced kitty for a total of $63,750.