Most people don't know that the Treasury Building is a big office building directly connected to the White House by basement walkways.

Because it's not the treasury building lol. There are multiple buildings near the White House that are under this umbrella, and I wouldn't think Treasury is one of them since they need their own office space.

Because it's about Eisenhower Executive Office Building

Why is this omission of any note? I know the building and I can tell you that it is not particularly remarkable.