I think I found a bit more information about that Galaxian3 attraction. The Game Engine they used for Galaxian3 Attraction could possibly be the Borland Program "Delphi 7" that Namco might have used to create this game, as shown in this image:
The same could be said for theater6 as well:
Notice the numbers on top right. It appears to be the number of frames for the whole length of the laserdisc. That can be said for the Galaxian3 28-player version. Also the one on the left of the frame number, It could either be the variation number or it could be the chapter number for the 16 screens. Regardless however, The laserdisc footage appears exactly the same.