If I remember correctly, the original patches for both Grim and Monkey4 include many significant bugfixes, and even back then it was not recommended to play the games without upgrading them first. In fact, according to its documentation, ScummVM won't even run the games if you don't include the corresponding patch among the data files. In case it can be of assistance, the patches can be downloaded directly from the ScummVM website:
https://wiki.scummvm.org/index.php?title=Grim_Fandango
https://wiki.scummvm.org/index.php?title=Escape_from_Monkey_Island (these are language-specific)
As a suggestion for the future, I'm wondering if it would be viable for DREAMM to handle these patches in a somewhat similar way. As in, the user provides the original game discs and the patch, and then DREAMM combines them to provide a fully-patched installation of the game which it can then run.