@cursedLight -- I get the simplest solution may be the correct one. However, this is Hata-sensei we are talking about.
[ol]
[li]If the little girl in the flashback is Tsukasa, it clashes with the notion that Tsukasa cannot be injured. The little girl had injuries.[/li]
[li]The flashback Tokiko remembers is from the POV of the little girl.[/li]
[li]The various splash pages have shown Tsukasa in various places and times on Earth throughout its history. Further, Tsukasa has spoken in a way as to imply she has experienced things from hundreds of years ago first hand. If that's the case, and she has not aged, then the little girl would not be Tsukasa. [/li]
[li]Tokiko could have adopted the hair and clothing style of the person who saved her. Hata-sensei hid the face of the woman in question. [/li]
[li]Tokiko could have made some ohagi for Tsukasa at a later point as a thank you. And she continues to do so all these years later as a thank you. [/li]
[li]Tsukasa has rescued folks before. One being Nasa and one being Chitose. So this rescue fits with her earlier rescues.[/li]
[/ol]
So while you may think, "You ignorant F's need to learn how to read!", in reality, the situation may not be as simple as you'd like to believe. So no sense in attacking others when you might well be in the wrong.