At first glance, this seems like a decision Fang Zheng made on a whim (though it is indeed the case), but Fang Zheng also thought it over before deciding to incorporate it.
The reason is the Mid-style magic attack.
This kind of magic attack can destroy objects without causing serious harm to life (of course, mental trauma is another matter). You see, this is something that can only exist in this world. After all, if you were to claim a "magic that can instantly vaporize a building but won't kill humans," people from another world might look at you as if you're an idiot.
And now, with such a good thing at hand, Fang Zheng naturally wouldn't use it for nothing.
The reason for choosing spell cards is, on one hand, Fang Zheng wants to pay homage, and on the other hand, it's a decision he reached after studying Mid magic.
