OS class is not about Linux, its about OS theory. You learn the algorithms for priority queues and preempting tasks and even build a simple OS (depending on the class). Very little of it is about how IRL operating systems/kernels like NT or Linux work, though they did use some examples to demonstrate. Forking was more in Systems programming class, but that class was more about C, system calls, linking, and gdb. Not much time was dedicated to the syntax of shell scripts.