I think CFA being closed on Sunday actually drives more business their way. Something about not being able to have something when you want it. I read recently their locations far outsell their contemporaries. It also must make scheduling far easier.
I could take it or leave it. Nobody eats there because it’s always packed.
Regarding the bold, that very well may be true.
Regarding the italics, I could see other factors in play.
Various public chains which operate on a more pure franchisee model I think tend to lead to higher density of locations than Chick fil A (which is private). According to Wiki, CFA builds and owns its locations. I can say that locally I see the same with In n Out (also private), which I believe also builds and owns its locations.
Keeping appropriate spacing between locations can lead IMHO to higher per-location sales numbers, and the locations being more crowded.
For example, below are the locations near me for Chick-fil-A, In n Out, and McDonald's (for comparison):



I'm going to assume that this leads to higher per-store sales because there are fewer stores.
Obviously McD's to InO is a direct comparison as burger joints, but I don't know of a good analog in this area for chicken-specific restaurants. We don't have a lot of Popeye's or KFC in my area, and Raising Cane's is relatively new to south OC as far as I can tell--I didn't see them popping up until maybe 3-4 years ago.