I would not assume higher pressure. The fan is blowing the cooled air (output) straight down into the plastic cover. The air at that point has to be extremely turbulant as is makes it's way into the outlet ports. By installing the RV Airflow device, the air is directed in a much smoother transition from vertical to horizontal flow and into the ductwork. I didn't buy the RV Airflow, I'm a DIY'er and used the foam project board to make my own. By my experience with airflow, and by observing the increased airflow out of the duct vents, my eductated guess is that there is less restriction and pressure drop. And, any efficiency improvements in cooling makes the unit work less overall. Just my opinion, no data, but some relavent experience.
2016 Hurricane 32N
2008 Jeep Wrangler 2D toad
Ready Brute Elite II tow equipment