This. We had to write a multi-process 68K assembly OS as part of an undergrad course. This helped immensely in having an idea of what the Linux kernel is doing. Without that - how do you even get started writing a kernel, if you don't know what it is or what it does?
you can "accidentally" write a kernel, at least in my case.
I was doing some embedded stuff when i was at school. I needed to run some "functions" in parallel. Obvious choice would be using a RTOS, but i did not know the exist of RTOS, so i spun up some timer interrupt, a "queue" of function to run parallel, an isr that acts like "scheduler", some variables that act like "semaphore", etc.
Only few years later i realized i have invented a very simple "RTOS"
