Squirtle has no general purpose for being shiny, I admit it would make more sense if it wasn't. The reason why Squirtle you encounter is shiny is the fact that I wanted to test out something new, that's all. Most of the scripts in the "beginning" of the hack are also tests to see whether something works or not (like the stairs in gyms and that kind of stuff).
Also, I'm answering to your question here because I usually tend to post updates along with saying something else. It's pointless to make people check the thread just for me saying what I pointed out above.