The data sheet says it's not a stand alone unit so it requires the other regulator to work. I tried looking it up, but the documentation is sketchy. In any case, its a lot of electronics to fit in a small box.
The problem with high power boosters in general is they require large input currents which means big unwieldy components for the converter. There's also more stability issues for boost versus step-down since there's an extra pole (a mathematical instability) in the feedback network. It's more work from a design standpoint and there's not much demand so you don't see high output boost modules.
DC voltage boosting is not something done much in the commercial world. Typically voltage has to step down from a 12V DC rail for high power stuff. That being the case, you probably will not ever find a small boost module able to put out currents upwards of 20A. It would be possible to design one with one of the available boost controller chips out there but it does require an amount of expertise in electronics design.
It's just more practical for high power outputs to use a battery of series cells and step down voltage rather than boosting voltage with a battery of parallel cells. The one big advantage for parallel cells is the ability to use USB charging, but it's not that big of a deal to use a balance charge connector and balance charger in lieu of a USB connector and USB power supply. That's of course if you want to be able to charge without removing cells from the enclosure.
