I don't find coffee in the coffee pot as evidence of breakfast. Our coffee pot does not get cleaned until we make coffee again, usually right before bed so it is ready to go the morning, or, the next morning if we forget or were too tired the night before.
Having coffee in the coffee pot throughout the whole day is not usual in my household. The eggs could have been recently purchased, or she made a scrambled egg for the boys for dinner. I did that all the time when my kiddos were young. And bananas on the counter.....well, we have bananas on the counter almost every day.
I personally don't eat popcorn for breakfast, but it is entirely possible it could have been left out from the night before.
I do not believe the house was staged. All MOO
But what were the McStay's habits?