It is true that WHILE GROWING, tortoises that are kept in conditions of constant low ambient humidity and/or dehydrating conditions are at high risk of pyramiding.
Keepers claim success at combating this by increasing humidity, frequent spraying of the tortoises shells, frequent soaks, maintaining a humid hide that the tortoise WILL USE, ensuring the tortoises drink frequently, or a combination of these.
It's probably true that most baby tortoises kept by novice keepers ARE pyramiding, do to popular advise of the last 20 years.