A question in constraint based analysis
Can you point to where this example comes from? It might help. 

I think the author is trying to express something a little different than what you're anticipating with this example. For instance, for a C programmer reading this introduction, this example would illustrate that "x 1" in the first line isn't like x(1) in C, it's more like (*x)(1) in C -- you're calling a function there, sure, you even know the type of the function you're calling, but you don't know which function. Certainly you are correct that in this example you can figure out "oh, it's either got to be the function associated with g or the function associated with h." But I posit that when you sort this out in your own head, what you're doing is just executing the program, which is of course the most straightforward way of "statically analyzing" any terminating code!

The example is small; any example that's going to be easy enough for you to straightforwardly understand is, almost by definition, going to be one where your brain can "statically" figure out the answer. The challenge that Control Flow Analysis tries to solve is working over potentially large programs, quickly and precisely.