The page addresses this issue, saying that browser text wrapping can cause issues and gives advice on how to deal with it.
The page says that “browsers may split a QR code across lines” - but this isn’t split across lines.
Experimenting, if I just type "[Q R]" (very short, so not likely to line-break), the problem still occurs.
If I inspect the element, and add `white-space: nowrap;` to its style, the problem still occurs (although the text doesn’t wrap!).