If you edit only the files in the GameInfo folder, then thats the only folder you need, and it has been that way since the tools were released. You edit a mesh, the whole folder has to go in.
Are you sure about that? If anything I've found the reverse.
I currently have a mod which changes mesh, textures, gameinfo, string. Right now it is stable with everything removed but its changes in mesh and textures. However, when I remove the Gameinfo things I didn't use, the game complains and crashes.
Or maybe you were talking about pre-1.03 - but you used present tense, so I'm confused