Comment by soraminazuki

Some kernel threads, besides the idle task, have PIDs other than 0? You mean literally all of them.

More crucially, kthreads are supplementary components of the Linux kernel. They represent just one method of running tasks asynchronously and don't represent the entirety of the kernel.

At this point you’re arguing over technicalities to somehow validate your objectively incorrect statements. The kernel isn't "special process zero," period. The kernel isn't a process. You can't rely on a process to implement the machinery required to run processes. Furthermore, the parts that do have PIDs aren't even assigned PID 0, except for the idle task.

If you don't believe me, just ask the kernel itself. There is no /proc/0.