But what if the students assigned to the less desirable building really were less happy, but they had made other changes to their life to make up for it? Maybe

But what if the students assigned to the less desirable building really were less happy, but they had made other changes to their life to make up for it? Maybe they spent less time in the building, or improved the aesthetics of their room, or spent more time on hobbies or socializing. I suspect confirmation bias leads researchers to find proof of their initial hypothesis without ruling out other explanations.