No, it's not faster. They are comparing a Go version that does not do character decoding (which is necessary for correctly counting the number of words under the presence of non-ASCII punctuation) to a C version that does decode characters (and matches them against a larger character set with iswspace).

This can be easily shown, by counting words and lines using wc separately. Word counting decodes characters (to find non-ASCII whitespace that may separate words), whereas line counting just looks for ASCII line separators:

    $ time wc -w wiki-large.txt
    17794000 wiki-large.txt
    wc -w wiki-large.txt  0.48s user 0.02s system 99% cpu 0.496 total
    $ time wc -l wiki-large.txt
    854100 wiki-large.txt
    wc -l wiki-large.txt  0.02s user 0.01s system 99% cpu 0.034 total

So, without character decoding, looking at every byte is ~15 times faster. So, if you'd compile wc without multibyte character support (which would be a fair comparison), it would probably beat Go without any parallelization.