CompSci is not engineering. It's almost math major, heavily on the discrete side of things.
In contrast, I know engineers who live and breathe PDEs and tweak compilers to solve them faster.
I doubt my CS professors would be able to solve a PDE..
Beyond the basics, not even many math professors can do that. Math is too vast and people specialize. Strong algebraic geometers are not necessarily strong analysts or algebraists or logicians.
1) No such thing as universal mathematician in this day and age.
2) Engineer's PDEs(algorithms) are not the same as mathematician's PDEs(theory). Same as comparing a student in China who learned English to communicate with English speakers to English majors from English speaking countries.