The Japanese pressings of everything are always superior. I discovered many years ago that the art books printed in Japan werre always superior to the same books printed in the U.S. The colors, the registration, the quality of paper -- in every regard, the Japanese books were far better. Then I began listening to LPs pressed in Japan, and realized that these were also much better than the same recordings pressed in the U.S. and often much better than the same records pressed in Europe. And that was particularly true with remastered LPs. Wow! They were so much better than the original American releases of the same recordings.
This trend has continued with CDs and SACDs. The Japanese take such great care in remastering the originals. I love Russian music, and I buy Melodiya LPs when I can find them. But Melodiya was erratic. Any time I see a remastered version pressed in Japan, I know it will be better. The same is true of popular music. The Japanese pressings of "classic rock" are usually far better than the versions released in the U.S. and often in Europe as well.
So, your review does not surprise me. We are all aware how good the Exton recordings are of Mahler performances.
The only difficulty is (1) availability and (2) cost. The Japanese pressings are often difficult to locate in the U.S., and as a result, the cost of obtaining them is usually quite high due to shipping from Japan. This is too bad, because if the price were about the same, the Japanese versions would be purchased more often, and it might force companies in the U.S. and Europe to upgrade the quality of their releases.