Interesting! I hate to lie to it but you gotta do what you gotta do!
I have lied to the AVR that I had 4 Atmos ceiling speakers when I had ZERO.
This was to check to see if I was getting Atmos decoding before I installed my 4 ceiling speakers.
Based on my experience with watching many Atmos and DTSX contents, having one Atmos speaker is better than zero Atmos speakers.
It seems like most of the time, what I hear from the four overhead ceiling speakers are rain, thunder, birds, aircrafts, voices, and music.
There are some panning effects and 3D sound-field creation, but being able to just hear something overhead is better than nothing at all.