As I understand it, scrappy is the only mod to add it's own variables and thus is detectable.
Actually... I've just made a proof of concept that detects Sancho Mod correctly.
I won't discuss technical details — not to give DPC bad ideas
Sancho didn't really do anything other than require it to be continued to be used. Which has caused it's own problems now.
Sancho provided a "save fixer". It's just a small
.rpyc file that you can drop in your game folder once you’ve uninstalled Sancho Mod (or if you're playing a new release for which a new version of Sancho mod is not available).I successfully played Episode 11 (for which, AFAIK, the Sancho Mod is not available) starting from a save made with a Sancho-modded Episode 10 game, just using Sancho's save fixer.