Dieterich identified it as a Mithraic initiation script in 1903 and Cumont rejected the identification, and no evidence has appeared since that settles it either way. The text carries a Mithraic name and solar imagery; it carries none of the iconographic programme that defines Mithraism in its archaeology, and it carries the Graeco-Egyptian magical vocabulary that Mithraic material does not.
What would resolve this A Mithraic ritual text of independent provenance, from a Mithraeum or another controlled context, against which the passage could be compared. No such text is currently known, which is why the passage was treated as decisive in the first place.
OpenHistory of ancient religion, Mithraic studies, papyrologyHans Dieter Betz, The Mithras Liturgy: Text, Translation, and Commentary