this is a very interesting read, thank you for posting

you may consider a simple example for yourself:

Portfolio $100,000.00 $60k into US Tbills, (3, 5, 10y) $40k into SP500 cash $40k into Sp500 on margin

$140k exposure For the portfolio to be wiped out, you would need to have a 50% drawdown in the sp500 which hasn't happened in 90 years, and that assumes in a crash your tbill face value wont soar due to rate cuts