Yes, math and physics majors will most definitely have to do a lot of study outside their fields if they want to get involved in software, as will civil, electrical, or nuclear engineers. However, I don't really see why math majors should have to learn properties of materials to demonstrate that they are prepared to write reliable software, any more than engineers should have to figure out how to pass an exam on real analysis, group theory, and topology in order to get licensed to write software.
I speculate the general engineering requirements exist because the most complex engineering projects require an interdisciplinary approach. The different disciplines need a set of shared concepts and language to work effectively. Thus the idea of an "Engineer" who is both a specialist as well as a generalist.
