"If you have configured a root password, the above blank password trick will not work."
So if root doesn't have a password, you can log on to root without a password. Isn't that how it's supposed to work?
That doesn't mean there isn't a bug, though - the bug is instead in the procedure for installing the operating system on the computer, which apparently fails to notify the user that having a password on root is recommended.
Oh, wait, Macintosh computers come with the operating system preinstalled, don't they? But isn't there still some sort of personalization program you go through when you use the computer the first time? That's what should be fixed; being allowed to not have a root password may be a feature that is too risky to leave in, but it isn't really a bug in itself.