To be more specific, you should not keep your money at a 3rd party with more control over your money than necessary for longer than necessary.

Giving PayPal an interest free loan and control over you balances rather than sweeping them into a (potentially interest bearing) account controlled by you is one example of this.

Another is having a second account at a different bank that you sweep money from the first one. That second bank account should be set up to reject automated ACH withdrawals so that you can push money into it but PayPal, your payroll company, your bill payers, or even other companies that ACH payments to you cannot withdraw from your account without your permission.

> That second bank account should be set up to reject automated ACH withdrawals

This is a thing? How do you do this?

Is a bank a 3rd party in this argument?

Yes. You should have more then one bank in case they lock your account for some random reason.

no, but you shouldn't keep your money in a bank either. Put it in an investment vehicle to at least break even with inflation.

the 3rd parties I'm referring to are things like work marketplaces like upwork, even gift cards or undeposited checks.

The most potent 3rd party is typically vindication and government laws giving it superpowers. They have more power over your money than banks.