That shouldn't be necessary if the air flow is kept low. I think the reason for including it is to allow it to run at an air flow comparable to conventional HVAC and thus be a drop in replacement.
Looking through the documentation, it looks like they use the desiccant solution to absorb moisture and then use "reverse desalination" to regenerate it. Reverse distillation is a great choice when there's a lot of "free" heat like solar thermal or heat coming off an engine or other device, but when there isn't, what about reverse osmosis?
Desalination - Wikipedia, the free encyclopedia