There isn't anything special about functions; the original article does not describe this correctly. Rather, the big conceptual difference is the point at which the expression is evaluated – once for the whole program (`=`), vs. at each call site (`=>`).

I presume this got accepted because it fixes a well-known gotcha with default parameters in Python due to early evaluation, where, for instance, the dictionary instance in `def fun(args={}): …` would be shared between all invocations, leading to all sorts of fun bugs. This is especially pernicious as most Python programmers will know other languages as well, where this tends to be handled much more sensibly (e.g. in C++, D, …) and default arguments are evaluated at each call site.