The edit wasn't only about whitespace. It corrected two things:
Anything that's not a shell command or some kind of code
should not be in backticks. The
Erase free space should have probably been Erase free space or "Erase free space". Folks really don't like to see this, as it distracts from the content and is just syntactically wrong.
Unit suffixes should be spaced. This is the norm for SI units, and while GB etc. aren't SI units, the same could apply here. But editing a post just to change from "4GB" to "4 GB" would be unnecessary.
The rules for "too minor" edits are less strict for users with edit privileges. We review edits for users <2k to have them work hard for their privilege, but after that, minor edits are fine unless they come in masses.
Even if a little minor, the edit shouldn't have been rolled back.