I haven't had a chance to look into this yet, but what you said sounds reasonable. I hear the map editor included with the game is very powerful - much more than what you would typically consider a "map editor". I bet it also has behavior mod tools, too.
I wish the game came with something approaching a real manual. All there is is a 14-page backstory PDF that pretends it is a manual.
I guess they don't want to step on the toes of all those companies that publish strategy guides for the game, such as
this one.
In many ways, both technical and superficial, SC2 operates more like a MMO than a typical SP/MP game.