The author uses the interpretation that Shiho disowns Miho not only because her style of tankery is incompatible with the Nishizumi way, but also so that Miho can be free to do things her own way.
Although Miho never expresses such a desire in canon, the author has Maho suggest that she wanted Shiho to be proud of her, which is why she stuck with tankery until the incident that forced her to save the drowning crew.
The author believes that weaker schools like Anzio have more of an advantage against Oarai, due to having to use more cunning tactics, and stronger ones will fall more easily against Miho. This is shown by how Oarai has much more difficulty against Anzio than Saunders in this fic, even though the opposite was true in canon.
Moral Event Horizon: Shiho visiting Miho in the hospital only so that she can disown her is this for many viewers.
Nightmare Fuel: Akio's father's plane crashing, and exploding in a large fireball is depicted somewhat vividly. And Akio saw this all when he was five years old.