I have a great deal of respect for the Barkers and the experience they bring. They are well respected in and out of the hobby most reciently being experts called on by USARK.
I also know they use the very best in controls and instrumentation. I am sure if she says 81 she means 81 correct. not 79-83 someplace. There is a high cost to get precision. Keeping a room at 82 perfectly is hard I would like to know what the exact range they have is. I have read lots of the comments they have made about the rising temps in the hobby Royals in particular. I believe them and I am sure they have it to work but I am also completely sure it is not as easy as it sounds.
Personally with a small collection I have each animal individually adjusted temp wise some have 88º hot spots and lower cool end temps others have higher based on how an individual acts and the shifts they make. All my animals use both hides typically 70%/30% splits. Although I trust the validity of the experience I am not sure it is prudent to suggest it across the board as signs of problems are not easy to spot for the inexperienced.