Huh, had no idea that the 2018 had cylinder deactivation. I have a 2013 and I got to drive my mother in laws 2018 for three days. Never noticed it turning on or off.
My 2017 Honda Odyssey on the other hand, holy crap! I got really annoyed with the vibrations and noise, as well as a noticeable delay in power. Found all of the 2011-2013 horror stories of failed piston rings, fouled spark plugs, etc on Odyclub. Newer models needing new motor mounts after 60k miles. I installed the VCMTuner on my Odyssey and it drives like a brand new car and handles so much better. Works by putting a resistor in line with the coolant temperature sensor. The temperature reading is lowered just below the threshold that would allow cylinder deactivation (or as Honda calls it VCM).
Odyssey is a whole different animal as it has a V6 though. I wonder if the CX5 could be fooled by a similar trick with temperature reading to not allow the cylinder deactivation (not that I would recommend it by any means on the CX5 at this point, lol!).