Ryllharu didn't just pull that explanation out of his ass, it makes perfect sense if you just calmly analyze the situation.

All of this is centered about, you guessed it, Railgun but being a spinoff in the same time span as the original you'll find certain repetitions of already seen events although under the perspective of other characters. That said, the story itself also has many exclusive arcs itself that any Misaka fan is sure to enjoy