It actually increments each word it finds, so while most words will turn to "1", "356" will become "357". I have to imagine this ending up in the blog is the result of a copy-paste mistake, a LLM hallucination, or something similar.

Others have commented on built-in vim functionality for counting words, but assuming the author copy-pasted a similar looking command, they may have intended something like:

    :%s/\w\+//gn

Knowing that the n flag will return a count instead of doing the substitute may be useful to know, but I personally don't need a search count very often.

Knowing that you can execute a vimscript expression on each search match using \= is also cool and I was unaware of such functionality. https://vimhelp.org/change.txt.html#sub-replace-expression