I just went through this focusing on any perceived differences.
The mono is the same source as the stereo but it is not a fold down. This is a custom mix with different EQ than the regular mix but I don’t think it was done with the same level of care as SW and ESB.
Here the first thing you notice is that the music levels are elevated higher than the stereo and the dialogue levels are also raised. What suffers are the sound effects which feel dialed down to being almost muted at times. You notice this most in the speederbike chase and how Lapti Nek sounds like a soundtrack mono mix release.

So this is a definite mono track much like hearing a 60’s album you’ve always heard in stereo on the abandoned mono mix that while not different is mixed in a way that is strikingly different at times.

Beautiful job Puggo! I ran this on my hdcrt screen upscaled to 1080i and on my klipsch towers.