I'm suspicious of this ritual:
1. It seems out of place in the corpus of public Golden Dawn rituals. There's the LBRP, MP, Rose Cross, Sepheratic Sealing Ritual, and the Hexagram ritual. Of the five, it's the only one that breaks from monotheism. It is the Hermetic order, not the Thelemic order, why all the Thelemic influence? While hermeticism is not confined to the judeo/Christian monotheism, it is a rather monotheistic system. Given the strong influence of kabala in the Golden Dawn, the other rituals make sense, with their use of the judeo/Christian God, the Hexagram ritual doesn't seem to "fit"
2. Crowley. It was Crowley who started releasing Golden Dawn rituals to the public. It was Crowley who founded Thelema. Crowley's disciple was Israel Regardie, Regardie's disciple was Donald Kraig. The bulk of what the public knows about Golden Dawn comes from these men, and Crowley is the fountain head. Could it be that Crowley reinterpreted the Hexagram ritual to line up with his new religion? Naturally his disciples would follow suit, and the rituals that have been handed down to the public would be corrupted.
3. Why the equation of the Egyptian God's (Isis, Apophis, Osiris) with the name of God IAO? It feels forced to me. If a primarily judeo/Christian order wants to use the death/rebirth archetype, why go the Egyptian route vs the Christian route?
I should finish by saying I have no access to Golden Dawn primary sources, which may explain all of this perfectly well. My intention is not to cast dispersions on Crowley, Regardie, Kraig, or Thelema, or any of their adherents.
If anyone has any input I would appreciate it. If any one is a member of the Hermetic order and you can discuss this with out breaking your oath that would be great.