Okay so the actual meaning is you don't stay outside of.the bank when there's no wanted inside the bank/ if there's wanted, rush inside and get it instead of camping outside. It's not that hard to follow this rules. If you want to catch bank robbers ,I've tips for you
Either you wait outside a couple miles away from bank, and wait for the "CRIMES : XXX BANK ROBBERY", then you can rush to the bank. Or you can just wait until they get into their getaway car and pursuit them.