Not really a planning issue. When the tour was that long and involved, very little else in MGM was built yet. No LMA, no Little Mermaid, no ToT...etc.
I do remember them making a BIG deal out of going to the bathroom before the tour started. There were no planned stops for the entire 2 hours. Even in an emergency, there were no restrooms to be found as you were really in the sound stages and there just were none.