I don't understand why the article recommends pivot_root. Its man page says that it may or may not change the current root and the current working directory of

I don't understand why the article recommends pivot_root. Its man page says that it may or may not change the current root and the current working directory of any processes or threads which use the old root directory, which means it can change the root of other processes! Also, it says that its typical use is for switching from the boot RAM disk to the actual root filesystem. This is an entirely different use case than chroot, and doesn't seem to have any security benefits either.