When you deposit money, you are lending it to the bank. That's not a metaphor. The balance shows up as a liability on the bank's books, because they owe it to you, and the money itself goes out the door as loans to other people.
At the end of the day somebody in that arrangement is holding the loans and collecting the spread, and it isn't the depositor. The bank pays you very little for your loan to them and lends the money out for considerably more. The gap between the two is the spread, and the spread is the business. Nobody's hiding it. It's on every bank's quarterly report under net interest margin.
There's no villain in this. It's a functioning arrangement and you get real things for it: the money is safe, it's insured up to the limit, and it moves when you tell it to. What you don't get is a return, and in most years you don't get anything close to inflation either.
So the question this strategy asks is simple. If the profitable position in that arrangement is the one holding the loans, can a household move closer to that position? Not by becoming a bank. By taking the two behaviors that make banking work and applying them to your own cash flow.
The first behavior is minimizing idle balances. Banks don't let deposits sit around uninvested, because an idle dollar is a dollar earning nothing while still owing interest to the depositor. That's what parking your paycheck against a line does: your income doesn't sit in a checking account at zero, it sits against a balance that costs you interest, so it's doing a job every day it's there. The math is in the one number that decides your interest bill.
The second is owning the asset that produces the spread instead of funding it. That's the piece that eventually points at a cash value policy, since it's the same instrument banks hold on their own balance sheets in size. That's covered here.
None of this makes your bank the enemy. It just means you should know which side of the ledger you're on before you leave six months of expenses sitting in checking.