No, I agree absolutely. I did say this was a study made for the California egg industry to find out, probably not how big an enclosure to give the hens, but how small they could get away with and still be considered "humane." It did lead to considerably bigger cages for the batteries until recently when California banned caged batteries entirely.I haven't read the study and you don't mention what the objectives of the study were. On the face of it it seems like yet another of those science studies that go something like we took two chickens, chopped the head off one chicken and it died while the other chicken carried on living.
Suppose the chicken, having pecked the enlarger looked at the result and though, well that's not any more interesting then what I had so I may as well have a smaller space within which I feel safe.
If instead they had constructed a run of a very limited size that thhe chicken could see out of and then offered the chicken to increase the size of the run, I wonder if the result would have been the same.
The Ex Batts on the allotment show a distinct preference to the lager run than they do to the smaller. They don't have to come out when I open the gate.