They are quite diligent in my experience, they’ve gone back and redone episodes on whims or by requests from people on the discord

I actually first started with the UTR/Joybell AI remaster which was better than the source files I had but was quite rough around the edges, especially the first season or two. Bright areas would blow out and show jagged lines, bleh

But this remaster is SO much better. Here is their workflow they keep updated so you can see what they do

There are comparison videos they have done as well, adding details like clearing up monitors and displays, etc

https://ds9redefined.wordpress.com/videos/