The Hatha Yoga Pradipika does not treat its postures as equals. Having reported that Shiva taught eighty four seats, Svatmarama singles out four as the ones that matter, and bhadrasana closes that short list behind siddhasana, padmasana and simhasana. Everything else in the chapter is described once and left; these four are the seats the rest of the book assumes.
That distinction is worth stating plainly, because the posture chapter of the Pradipika is brief and instrumental. It exists to arrive at a body that can be sat in without moving while the breath practices, the locks and the seals that fill the remaining chapters are carried out. A posture the text elevates is one it expects to be occupied for a long time rather than passed through, and the four it names are all low, bound and symmetrical arrangements that hold the spine upright without the hands doing any work.
To bhadrasana Svatmarama attaches the claim that it destroys every disease. That claim is the text speaking, and the atlas records it as the text's rather than as a finding. Claims of this kind are ordinary in the hatha corpus, which routinely presents a posture together with what it is said to accomplish, and reading them as therapeutic statements in the modern sense mistakes the genre. The Gheranda Samhita, working two centuries or so later, keeps bhadrasana among its thirty two but describes a different arrangement of the feet, which is one of the clearest cases in the corpus of a name outliving the shape it was attached to.