A Sant Mat initiation, called naam diksha or naam bhet depending on the lineage, is the point at which the tradition's actual meditation instruction is transmitted, and it is not published. A living master or an authorized representative gives the initiate a small set of names to repeat in meditation, together with the specific instructions for the practice, seating, attention and breath among them, that make the repetition into surat shabd yoga rather than an ordinary devotional exercise. Introductory writing from every Sant Mat organization explains what the practice is for and describes its stages in general terms; none of it sets out the instruction itself, which a follower receives only by asking for and undergoing initiation.
The atlas records this as a restricted tradition on that basis: the movement's own general teaching, its history and its account of surat shabd yoga as a method are openly published and are what this page's description and the article above describe, but the initiation instruction that puts the method into practice is transmitted individually, from a recognized master or representative to a prepared initiate, and is treated by every major lineage as something that cannot be taken up by reading alone. This is a genuinely different case from a text merely being old, untranslated or hard to find: the material exists only inside a living relationship between teacher and student, which is the same shape of closure this atlas already records for other initiatory currents such as Vajrayana empowerment and Shri Vidya diksha, and it is recorded here for the same reason, so that a reader understands what kind of knowledge this is before assuming a book could supply it.