After further comparison, the THX disc for TSWLM centers the dialogue AND score. The 5.1 was done and I believe the stereo matrixed PCM is a downmix. Why or how this was done is unknown or whether it is more accurate. Honestly I don’t think it is. Bond '77 in the PTS clearly shows the score being centered, as the opening bass notes are firmly centered as are the cymbal crashes in the chase. These were all panned hard right in the older release. It sounds as if they went back to the elements and played with the mix configuration in the 5.1 format.
Direct comparison to the older WS LD reveals the former as having a much better stereo spread and despite having some distortion and noise it is preferable I think. The film was supposedly a matrixed stereo release without Dolby encoding. No details of 70mm blowups have ever arisen.
The THX remaster has far better color and detail. The source transfer is identical, right down to the frame wobble in Gogol’s office after the titles. The THX DVD is a port and the SE is as well, though it may suffer from some additional processing.

Edit: the dts hdma on the Bluray sounds better than the 5.1/2.0 remixed track. It still centers everything but has far better clarity and detail in addition to better stereo imaging. Which is correct centered or not is unknown. Also the 2.0 track is the same as the thx LD.
The hdma has the original film version of the song.

This makes 4 mixes:
Original WS LD surround
Thx remaster 5.1/2.0
UE remastered 5.1 in Dolby/DTS with soundtrack title song
BD dts hdma remastered 5.1 with original song reinstated.