I wish I had a better explanation for why this is, but now you too have seen it first hand. I'm also not one to just believe anything some guy on the internet says, so I never get upset with people for doubting these things. I'm glad the info helped your tortoise.I know how you feel. I had this same conversation on this forum a few weeks ago and was directed by Tom to bring mine inside. I have to tell you and @Tom that my tort has definitely grown more and added some growth lines per week then he was doing before. His behavior is also different. He is alot more active and spends more time under the basking bulb. He even goes to his cool side now which he never did before. I use coco coir mixed with topsoil. I just wet the substrate once or twice a week and it maintains humidity of at least 75 -80 %. Mine is also almost a year old. I've have had him in an enclosed box since I got him in January so he hasn't had any pyramiding.
These breeders and tortoise experts on this site are amazing! Take their advice. They are passionate about educating new owners and have proven results. I am grateful!