Hitsuji Gamei (the author) is, for all intents and purposes, an extremely low budget Kinoko Nasu (creator of all TYPE-MOON works). He seems desperate to differentiate "real" or "serious" magic from typical Isekai game style elemental magic, e.g. casting Fireball level 100 using a videogame menu with a fancy chant.
Unfortunately for all of us, while Nasu poured over historical facts, trivia and mythology in order to give the FATE stories actual depth, and provide their magic with a proper folklore background, Gamei's "I'm not a hero" hero has absolutely none of this. Amusingly, he ends up casting vague groundless spells with no basis in the same manner as the boring Isekai residents he was so quick to demean.
Ultimately, when compared to the creator he is trying to mimic, the Author is a small child trying to wear his father's suit. For all Yakagi's attempts to cosplay a magician from the Clock Tower, throwing around Mercury like he's Kayneth El-Melloi Archibald, he has almost none of the background research to cover him.