This caught my attention:

Imagine a world where your “checking account” is actually a high-yield instrument backed by over-collateralized loans against Bitcoin. You are spending stable currency, but the backing is hard money.

I guess the stable currency would be the bank's digital dollar mentioned earlier.

If a bank can issue a digital dollar that is over-collateralized by Bitcoin, that digital dollar is “harder” and safer than a digital dollar backed by fractional reserve fiat lending.