It's an example of tunnel vision. The person who did this was having problems with chatter and the scalloped face it causes. He was so frustrated dealing with it he stopped thinking about how much metal he was removing. Noticed the problem only when installing the BB assembly. BTW- this is not the only time I've seen overly faced BBs (under 68mm or so), it's just the record (that I know of).

Folks hear so much about facing a BB shell, that they often lose sight of the need to stay at the 68mm width.

Often I'm presented a BB that looks like it might be faced and is already at 68mm. If I have a reason to worry about whether the face is square, I test it with a disc covered with fine emery, that replaces the cuter on my facing tool. In 2 turns I can have good confirmation of the face without removing any metal or paint to speak of.