I do not want anyone to be required to prepare to play a map. Maps should be designed well enough that you can just start playing and clearly see what is possible on the map. The strategy and decision-making parts of the game are what should be emphasized and things that get in the way of them should be reduced. Where you can and edge build or not is just a game/map rule, making the decision to edge build somewhere is actual gameplay. If you don't know the rules of a game you are unable to play or enjoy it to its full potential. It is the job of a game designer or mapper to clearly communicate the rules to the player. It is the job of the player to reason about those rules and try to make smarter decisions than their opponent. Making the rules hard to learn and forcing the player to intensely study the map or game code beforehand is just stupid.
Anytime I have to actually send an engineer/ACU to see where I can edge build, put my ACU in the water to see if it gets covered, check if a unit can travel over a hill, fire TML into a mountain to see if it works, or some similar activity I am taken away from gameplay and sent back to the rule learning phase. I consider these to be failures on the part of the mapper to effectively communicate the rules. Mappers have an extraordinary responsibility because so much of this game is map-specific. It seems to me that most of them do not understand this responsibility and just throw random stuff together.