The Mind, Body and Spirit layout is a three-card spread whose positions come from a scheme of the person that is much older than tarot and much wider than it.
A threefold person
Dividing a human being into a thinking part, a physical part and a spiritual part is a commonplace across many traditions, and the specific three-part vocabulary used here entered general English usage through nineteenth and twentieth-century religious and therapeutic writing. It is not a tarot doctrine and it is not derived from the cards.
The atlas records the layout's positions separately and records its authorship as unknown, which is the case for nearly every spread in circulation.
What that borrowing does
Because the three categories come from outside, they do not carve up a situation the way a tarot reading otherwise would. A card in the body position is being asked about health, work and material circumstances at once, which is a broad remit for one card, and readers vary in how they narrow it.
The advantage
Three positions that are genuinely unlike one another are easier to keep apart than three positions in time, and much easier than five aspects of a single self. That is the practical argument for this spread over other three-card assignments, and it is why it is commonly recommended as a regular check rather than as a spread for a specific question.