Controller doesn't drop to float

I'm using an RNG-CTRL-PWM10DB dual battery controller with 9Ah SLA batteries and a 20 watt Renogy panel. The controller bulk charges the batteries at about 14.4 to 14.8 volts depending on temperature, which it should. But after the batteries are fully charged, the voltage never drops to the 13.7 volt float voltage specified in the manual (Table 7, page 16). From everything I've read, a fully charged lead acid battery shouldn't have 14.4 - 14.8 volts applied for a long period of time. Other chargers and controllers all properly drop the voltage to a lower float voltage value of around 13.7 volts when the battery is fully charged, but this controller does not. I get the same result with a single battery, and the SLA battery type is correctly selected.

I called Renogy technical support and the representative said that this is normal operation for this controller and that the "Float voltage" shown in the manual is meaningless. If that's true, I'll steer clear of Renogy controllers and recommend that others do, too, since this behavior will certainly shorten the life of any battery it's connected to. But I'd sure like a second opinion on whether the design is actually defective or I just have a defective unit.

EE