It does not quite work like that.
With that converter pushing 1440 watts at just 24 volts, the internal Titan 2 KWH battery will start supplying power until it runs down to 24 volts. That is probably a little below half of the capacity. At this point, it will begin pulling power from the step down converter from the 48 volt (51.8 volt nominal) and the battery in the Titan will basically just sit there at this state of charge. So the inverter will be able to pull up to 1440 watts at this point without dragging the internal battery any lower. We don't know for certain how the DC-DC buck converter will act if you try to pull more than it's rated 1440 watts. It might just drop a bit in voltage and limit to the power, or it could shut off. If the voltage just drops, then the internal Titan batter will again start supplying more power, but it is already getting low. If the converter shuts off, then the Titan battery will get hit with the full load and you will not have much time left. It will hit low voltage shut off. But then the converter may power up again, and you end up with it kicking on off on off etc.
Basically, don't pull more power than the converter from the 48 volt pack. Even earlier, when the Titan has a full charge, you are still limited to the capacity of the Titan inverter. I think it is something like 2,000 watts. If you do need that kind of power, you may need two of the buck converters to keep up with the demand.