Installation source missing 'machine/_types.h' FreeBSD 12.2-release

I was attempting to install the latest FreeBSD display driver from nvidia's website, when I received an error from within FreeBSD's source directory:

/usr/src/sys/stddef.h:36:10: fatal error: 'machine/_type.h' file not found
#include <machine/_types.h>

I used the FreeBSD-12.2-RELEASE-amd64-memstick image to install FreeBSD, verified the checksum was right, and then selected to download src in the installer, so I am curious what could have caused the missing source files.
It's the exact same driver, but the port has some patches to make it work better. The NVidia driver replaces a couple of Xorg libraries, the installer from NVidia itself will just overwrite the originals while the port installs them separately and adds some mappings so the correct libraries are loaded. By using the port/package it's also correctly registered with the package database, and you can keep track of the version. A package is also supposed to have a good file list, so when you remove it you can be sure everything is correctly removed and there are no left-overs.