Let's get this straight, i did all this 7 years ago:
1) The Japanese Odeon marked RM *is* pressed fron the same UK stamper as the Harvest UK SQ. So, there is no true RM version.
2) Visually compared both Jap and UK lp. I have the Jap, i borrowed the UK from a friend. Same stampers, and IIRC Jap didn't even bother to add the EOZ n.
3) Both UK and Jap does decode identically.
4) Both UK and Jap, when decoded as SQ, have the same sonic placements as the discrete UK Q8, which i have.
Here's the tricky part:
5) Both UK and Jap, when decoded as QS, doesn'have the same sonic placements as the discrete UK Q8, however they do create a very nice surround landscape - even if it is a wrong one (for example, DSOTM SQ doesn't decode so well in QS). So i can understand well why it seems to be a true RM when it is not - even decoding it wrongly it sounds nice.
A especially revealing snippets is on "Summer 68": on the discrete UK Q8 the DG guitar pans from full front to Rear Left (going with memory... don't have a surround rig now where i'm typing). Decoding the matrixed LP as QS, that snippets show how astray is a technically wrong decoding, no matter how nice the end results can be.
Now, is someone want to buy a "pricy RM" version of AHM, i can sell mine.