I looked into that project issue your referencing. There is absolutely zero mentioning of zig labeled blocks in that exchange. There is no misunderstanding or confusion whatsoever.
It's a formatting bug with zig labeled blocks and the response was a screenshot of code without one, saying (paraphrasing) lgtm it must be on your end.
See the first screenshot in the exchange with newlines breaking up the label and block - and maybe this for proper formatting https://zig.guide/language-basics/labelled-blocks/