Just guessing here but “right sized” might be relative to historic temperatures and don’t take into account the extremes? In Arizona 117 is common enough that

Just guessing here but “right sized” might be relative to historic temperatures and don’t take into account the extremes? In Arizona 117 is common enough that you’d expect the AC to handle it with no problem but Texas it probably isn’t that common (guessing). Think the hottest it got since I’ve lived there was 122. People also commonly don’t cool their houses too low because it gets expensive, my sister used to have a McMansion and their AC bill was a lot (something like $400/month) and they were only cooling to around 78 or so.