Even something that simple falls into what vs why: You can tell it was spacing from the diff, so the commit message should be "linting" or "alignment" or something similarly more meaningful.

The diff may not be visible. The person might be doing a complicated cherry pick or merge and scrolling through hundreds of commits. If the message explains it, it saves them digging in.

My analogy is your bookshelf books still need jackets!

First line is for what, the rest of the commit message is for the why - if needed.

As for "spacing", you can probably tell the why from the diff as well. The "what", however, tells you whether it's even worth opening the diff.