Isn’t the Fourier series fundamentals generally a required course in undergraduate college EE field?

Of course. It's taught in both mathematics courses as well as engineering. The Fourier transform and it's digital domain cousin, the discrete Fourier transform play such a fundamental role across nearly every engineering discipline as well as physics and many other scientific areas, you cannot get through school without learning about them.

Yes, but how many software engineers remember any of that? Most aren't using it.