The problem: a patrol log proves nothing
Most patrol records are still a signature in a register at the guard post. The register shows a name and a time, both written by the person whose work it is meant to verify. When a client asks whether the 2am round actually happened, there is nothing to show them beyond that signature.
This matters commercially, not just operationally. Patrol frequency is usually written into the service contract. If a break-in happens on a shift you cannot evidence, the dispute is about your word against the client's CCTV — and that is a contract you tend to lose.