The English is a bit broken in the top-level comment, but both static content and proxying are clearly mentioned as "nginx things", which is entirely fair. If you don't consider proxying to be included under the term "serving" (which is entirely reasonable and not uncommon) this is entirely true - the only kind of "serving" nginx is good at is static files, the rest of what it's good at isn't "serving" but proxying to other servers that render dynamic content - PHP-FPM is one such server (it just happens to not speak standard HTTP).

I don't see why people always get mad when this gets brought up - I've always considered that to be a good architectural choice for nginx. Running application code in the webserver process isn't a good idea anymore so the focus on good static and proxy performance is actually what I think made it ultimately "win" over Apache - the industry has moved on from the old ways and Apache fell behind.