Not sure this is quite accurate. My memory is it was not in the Masterpiece set, which is why I bought the UK Blu-ray back then, which definitely had it. I do think they included the original mono mix when the standalone Blu of Psycho was released after the box set.
Hmmm, you could be right. I have the one from the Masterpiece set and it does have something that’s labeled as mono on it. I haven’t checked since this thread to see if it’s a real mono or a fold down.
I don't recall (all) the exact details now, but I also opted to import the UK edition instead of American standalone version back in 2010(?). A quick check only indicates that the American version came w/ lossy DTS mono instead of lossless DTS-HD MA mono as being the diff -- and IIRC, that was likely a significant enough issue for some of us at the time.
_Man_