"How do you know that the pitch is not true on one or more of the CD transfers?"
I was wondering the same thing. This may be naive of me, but I've always assumed that major record companies are very careful about correct pitch in producing CD/digital transfers of older recordings from tape sources, including cast albums. Because of the nature of digital playback, if the pitch of a recording on CD is off, that would have to mean the speed of the tape machine that was used to play back the original master tapes in making the transfer would have had to be off, which I suppose is possible.
I own hundreds of recordings on CD, and I think I've only come across two transfers that were notably off pitch: The first CD release of GOLDEN RAINBOW, which was also in mono (I believe that one was produced by Steve & Eydie themselves) and a transfer of the Victoria de los Angeles recording of the opera MANON that was, I believe, on the Testament label. (I very recently found a copy of the EMI release of that recording, and the pitch is fine there.)