I have checked a few beta sites and they are all like this. When you click on "Puzzling beta" it takes you to the site's front page. But you can move your mouse very far to the right of it (as far as the red X in the screenshot) and still click on it.
Non-beta sites are not like this - you have to click directly on the logo. You can't move the mouse away from the logo and still click on it.
This is the web inspector highlighting:
And this is it with 100% width and height, and 10px padding, with the CSS changes: