The AP version I have is actually a 4.1 DVDA I believe. Whoever created it must have applied a low pass filter to create the sub channel. Up till now, I was unaware of any other 5.1 upmix. I cant see how adding a faux center channel might improve it, and why degrade the resolution by subjecting it to lossy DTS processing?
From the description of it being silkscreened, etc, it certainly has to be an illegal bootleg. And I'm not sure at all that it originally came from "the vaults of Alan Parsons", but it is the AP mix.
I always thought the AP version we usually refer to was just the master quad tape (or an early gen copy) used for the quad SQ encode and Q8 duplicators back in the 70's. I never compared the AP DVDA to the Q8 conversion. I just assumed they were the same mix. Maybe not?