That was one ethos that was taught at the UC Davis CS program in the 90's-00's. They had clusters of IRIX, Linux, Sun, HP-UX, and (sometimes) MINIX boxes. Homework and lab projects would be nondeterministically graded on any except MINIX. It was also beneficial to add portability for Windows with MS and/or Borland toolchains for some projects. BSD sockets was pretty cross-platform with some idiosyncratic gotchas per platform.

It saddens me whenever someone or a group religiously tie their opinions or assumptions to a particular platform and irrationally scoff at others or refuse to consider that other things exist, are used, and function.