An anamorphic transfer would yield better results than most player-based zooming/upscaling, but its really besides the point that the transfer itself sucks because its from 1993. I have lots of non-anamorphic DVDs but they look fine because the transfers themselves are good, they yield considerable detail (and since I don't have a widescreen TV anamorphism is an irrelevant issue). The only version of the Abyss that you can get on DVD is non-anamorphic but it looks really good in spite of that.

The issue really just comes down to: the GOUT was an extra that was thrown on "as-is." The 1993 transfer is non-anamorphic so the GOUT is non-anamorphic. End of story. No work is to be done, the main point of the release is that the films are available individually, this is just an extra being tossed on to get people to buy, along with a demo for the latest video game of the time. Lots of extras are non-anamorphic, perhaps even most extras, at least back then.

Why are the menus anamorphic? Because DVD authoring software is anamorphic by defeault. Making anamorphic menus takes no additional labor, you just tick the box that it is 16:9 and this is the default that you start with.