I don't know that it's meant to shill the product -- rather, that's the tool that he has handy. I work all the time with Python, and frequently open an IPython shell to do some quick math ("what's the average of 4d6 pick 3?" "what is X% of my paycheck?" "how much do I need to contribute to max out my $FOO?"), simply because it's easier than a calculator.

I mean, sure, it's advertising Mathmatica, but it doesn't seem to be unecessarily doing so. It's more that it's ${programing-language-of-choice} for the author.