The line in question is from the Stella Matutina version of the 0=0:
"The Red Cross above the White Triangle is an Image of Him Who was unfolded in the Light."
In my article I pointed out how I saw the above as referring to Christ, and since this line does not appear in the original Golden Dawn or Alpha et Omega variants it is clear that it represents part of the Stella Matutina's approach to the subject, which was considerably more Christian than the other two orders.
This is also supported by the Stella Matutina variants of the Z-documents. For example, Z1 tells us:
"The Red Cross of Tiphareth (to which the Grade of 5=6 is referred) is here placed above the White Triangle, not as dominating it, but as bringing it down and manifesting it unto the Outer Order; as though The Crucified One, having raised the symbol of self-sacrifice, had thus touched and brought into action in matter, the Divine Triad of Light."
The reference to "The Crucified One" and "self-sacrifice" can easily be interpretted as being Christ, and I would find it surprising if someone did not recognise this as a possible and valid interpretation. It is not explicit, in that it does not literally say "Christ" within the text, but the implication is there, as it is (or can be seen to be) in "Him Who was unfolded in the Light".
For those who would argue that "The Crucified One" here does not necessarily refer to Christ, I believe the next line from Z1 is fairly revealing:
"Around the Cross are the Symbols of the Four Letters of the Name Jehovah - the Shin of Yeheshuah being only implied and not expressed in the Outer Order."
Yeshuah - Jesus - Christ. Now clearly this is referencing an esoteric view of Christ (as one would expect from an esoteric order) which is implied, but not explicitly expressed, in the Outer Order. This is not to say that the Outer Order is suddenly Christian in focus or symbolism, as it is clear that it is not. I see the Outer Order as overtly Osirian and the Inner Order as overtly Christian/Gnostic/Rosicrucian (ultimately I label this "Gnostic"). There is a very clear distinction between the two, and it is not my intent to muddy that distinction or to bring Inner Order material into the Outer or vice-versa. The distinction, however, does not prohibit the potential that the Osirian may allude to the Christian or the Christian to the Osirian, and that the the Outer Order material may allude to the Inner (a bit of foreshadowing, if you will) or the Inner to the Outer. This allusion is, of course, subtle (as all allusion is) and does not reflect the overt nature of the material or each of the two Orders.
The Golden Dawn system is ultimately and quite obviously syncretic in nature, which means that it has merged and reconciled many widely different things into one complete system. In some areas it has done this really well, while in others it is a little lacking. However, it is my opinion that when it comes to the Osirian and Christian mythos they have been merged very well, to the extent that a Pagan may see the Christian references as pointing to Osiris and a Christian may see the Pagan references as pointing to Christ. And they can be both simultaneously without contradiction, as well as being many other things that fit the system. Thus, this is certainly not the only viable interpretation, but one of many, and they are all equally valid, even if we individually prefer one over the other (which is our right).
For more on this topic I would recommend the latest post by Sincerus Renatus on his blog Gyllene Gryningen, which covers some of my points and expands upon them with additional material and insights. It is well worth the read.