It probably uses a triac as the switching element, which is not a simple switch. For example, it may have difficulty with reactive and electronic loads like motors and CFL's/computers.
The other quirk about triacs is that they latch on until the current stops. There is a threshold for that latching current, which when multiplied by the expected voltage, produces a number for power. I alluded to this here, but didn't actually say it: https://electronics.stackexchange.com/a/148084/53375
If the controller were to hold the triac on like I described in that other answer, then there would be no minimum load, but if it only "bumps" it on like a traditional manual dimmer, and relies on the latching behavior to do the rest, then there is.
If they're actually serious about the minimum load, and you give it something less, it may flicker with the "bumps" that try to turn it on, but will never be fully on. Anything besides an incandescent bulb, pure heater (no fan), or dirt-cheap LED rope light (the kind that has a bunch of LED's in series with a single resistor and clearly flickers at the line frequency when you wave it) will likely hate you for that.
I would recommend a mechanical timer for that circuit. It'll use a synchronous motor to drive the mechanism, so it's as accurate as the power line, which itself is tightly controlled simply to keep all the generators in sync across the country. And the important part is that it'll use a mechanical switch that really is simply on or off.