I don't think George Stevens intended his film to be seen on Blu-ray either. Sightly different framing (when the theatrical aspect ratio is the case) always has been part and parcel of remastering films for the Home-Video Format. As I mentioned, director's adjusts shots framings all the time when a new transfer is redone.
If it was released in theaters botched and savagely reframed (I assume by zooming to 1.66 and adjusting to the top of the frame to prevent looped heads), then there's no point in reproducing this on Blu-ray. (You can probably do this by zooming your DVD and adjusting up, to see the results).
That a choice was made to adjust shot by shot (or in some shots) shows effort was made to make the framing natural and not noticeable by current audiences. It can be only good because you get the theatrical aspect ratio, looking the best it can be on home-video.
Remember, it was the first widescreen shown western (unless I'm mistaken)
Would this release have warranted an extra 1.37:1 version? By all means, since the film was shot in one intended ratio, and shown in another.
Do the new 1.66 violates the film format history? I don't think so. With the involvement of the son of the director, it will probably constitute a definitive, archival version of the theatrical format of the film. It's not like the film will be mastered in varying aspect ratios (IMAX style). They have chosen to preserve the theatrical 1.66:1 format.
What they put within this framing, should be what looks best to the compositions of the film. That's the choice of the guy in charge of the new transfer, and you can't dispute it anymore than you can dispute a director adjusting some shots in new transfers. Their aim is to put out a best presentation, not ruin the movie. Quite the opposite.
Think of it as cosmetic changes. It's not at all like they are putting Jabba the Hut back in. They just want the best version possible in whatever format the film was initially shown theatrically.