The first C program in the blog post allocates a 256kB buffer and writes that one exactly once to stdout. I don't see another loop which writes it multiple times.
There's an outer while(true){} loop - the write side just writes continuously.
More generally though, sidenote 5 says that the code in the article itself is incomplete and the real test code is available in the github repo: https://github.com/bitonic/pipes-speed-test
