, I forgot one important word.
Me (coffinbone): "The thin wall will disappear as entire hoof is rasped shorter."
Correction: "...as the entire hoof WALL is rasped shorter."
The sole was already mistakenly gouged out with a hoof knife. As the hoof wall is shortened, a crescent-moon-shaped sole callous will appear at the toe, and deep laminar grooves will disappear (LF inside edge). In the current trim you can see a small sole crescent from rasping the hoof wall surface, it just needed more. It helps support the horse, per Pete Ramey.
In the cited article, Pete Ramey says:
"The horse was never intended to hang from the laminae. The hoof walls, soles, bars and frogs are supposed to work in unison to support the horse. Trimming and shoeing practices that force the hoof walls to bear all of the force of impact create more constant stress than the laminae were ever intended to withstand." Pete's very clear, and awesome :)
If the hoof walls are too long, AND the sole was knifed away, his bones may have no choice but to "hang" and "force the hoof walls to bear all of the force of impact..." His weight will drive the bones and inner structures toward the inaccessible ground, because the walls are holding up the whole horse.