This was discussed extensively on another board at the time of release. The consensus IIRC is that they are indistinguishable from the original CD releases supervised by Thomas’ mother. As such it was considered a disappointment. However, there may be some new material not released on CD originally
The 'restoration" spoken of is likely the restoration of the original analog tapes. Mercury, unlike most other companies, did not prepare a master tape for the disk cutting and later for the CD transformation (though the Golden Imports did). They always used the original session tapes. These tapes were handled, and perhaps mishandled repeatedly and were said to need a great deal of care to make them usable for yet another series. Apparently they needed a good bit or cleaning off of old glue and re-taping.
Notwithstanding, I think I have a high resolution system and I think the sound of these old Mercuries is fine, though some are much better than others. That was also true on the original CDs, and on the LPs.
In any event they are all up on Qobuz so you can make up your own mind.