The A A published its own curriculum, including the Probationer grade's place at the head of the sequence, in The Equinox, the order's periodical, making the grade's existence and general requirements a matter of public record from early in the order's history rather than something documented only much later, unlike the Golden Dawn's comparable First Order material.
General accounts of the A A's published structure describe Probationer as a period of preliminary study and self-assessment before a candidate is admitted to Neophyte and the numbered grade sequence proper, a framing drawn directly from the order's own published curriculum documents rather than from outside reconstruction.
Because The Equinox was a public periodical rather than material restricted to members, Probationer's position and general requirements have been part of the public record on the A A since close to the order's own early twentieth century founding, a transparency general histories of the order treat as a deliberate departure from the Golden Dawn's own more closed nineteenth century practice.
Scholarship on Crowley's organizational choices treats this public periodical model, publishing grade structure and general requirements openly rather than keeping them internal, as a documented and deliberate break from the older order's own practice, not an incidental difference in style.