Hi, Mark:
Well, I'm not aware that Harrison ever gravitated toward any direct implication of the Mount Temple as a potential "mystery ship". (But then, nothing I've seen written about "A Titanic Myth" has compelled me to part with the collosal asking prices I consistently find. So there I have to plead ignorance.)
I know that in the original 1962 MMSA publication, "The Californian Incident: An Echo of the Titanic Disaster", Harrison (as editor) retained Lord's exhibits of the original correspondence that had indicted the Mount Temple -- a decision that caused quite a stir in the MMSA community. But at the same time, Harrison expressed serious doubts about the plausibility of any such suggestion ["Foreword"]:
"Secondly, several references are made in the attached correspondence to the possibility that the Canadian Pacific liner
Mount Temple might have been the ship which was seen to approach and recede from the sinking
Titanic, ignoring her distress signals. Navigationally, this appears to be an impossibility, any suspicion which attaches to her being based upon the allegation that green lights and distress rockets were observed from the
Mount Temple during the morning. I consider that the most likely explanation of such lights is that they were the signals exchanged at the last moment between the approaching
Carpathia and those in the
Titanic's lifeboats, but confirmation of this point will never be possible."
(Actually I'm pretty amazed at that, since it constitutes one of those rare instances where I agree with Harrison's conclusions whole-heartedly!)
By the time of the "Petitions" proper, Harrison would seem greatly disinclined towards any accusative posture. There he embraces the Mount Temple evidence as corroborative of the error in Titanic's CQD position and employs this in support of Captain Lord's reckoning of the lifeboats' last position. So my suspicion, at least, is that Harrison would have been extremely unwise to subsequently cast aspersions on Moore's veracity. (I could be wrong.)
But I have encountered remarks that strongly insinuate the Mount Temple as a "likely" culprit. (I don't mean your own, of course.)
Plus, in a remarkable about-face from Harrison's assurances regarding Moore's credibility, Captain Collins ["An Ice Pilot's Perspective"], who does NOT ultimately find Captain Lord entirely blameless *or* propose the Mount Temple as a "mystery ship", nevertheless paints a very disparaging picture of Captain Moore in efforts to bolster his own contention that Boxhall's CQD was entirely accurate.
The Californian saga and its spin-offs certainly do make for strange bedfellows at times! ;^)