But the bottom one is still a QR code, it's just an out-of-spec QR code. Most QR readers will still process it just fine, but there's greater room for error depending on what surrounds the code itself.
i hate coding for browsers. To that end, I do not actually know css. I just called it padding when I wrote my own qr code library, because it was easier to say than "quiet zone".
Just like "dots" or "pixels" are easier to say than "modules"