It is a heat pump, but the defrost cycle is not needed because it is still in the cooling mode until it reverses for winter in the heat mode.
Good point on that delay being in the thermostat, thats probably it.
The customers original complaint was that the A/C breaker trips 7 or 8 times a day and an A/C guy check it and said it was ok.
Its still hot here in AZ so it runs a lot still.
The Golden Rule - "The man with the gold makes the rule"