That app is able to fix disc images so they are stealthed and prevented you from being banned from xbox live. It makes the disc appear in the same way an original does. ABGX has stealth files which are basically the xbox game disc video partitions, these are different sizes so the layer break changes, it's able to detect if your game image is xgd3 or xdg2. There's lots of other options and things it can do such as fixing disc images, extraction etc. I am surprised you never had it as it was always a big deal in the xbox360 era.
If you want to check it out:
https://abgx360.hadzz.com/