Thinking the stadium building and the stadium as an entity are the same is understandable and seemingly a common misinterpretation. I hope you can understand the way I've mapped it, as it applies to much more than just stadiums. If you’re unsure as to why certain tags have been moved in this instance then please say and we can discuss it further.

Treating the parking, pedestrian grounds, etc. as part of the stadium area, like you mention, isn’t invalid by any means. These boundaries are usually harder to define than the outer perimeter of the physical stadium building, which might be why it has become the standard.