Another thing to point out that I mentioned before in the NMAiE general >>6435 is that The Parent Map displays the backstory of both Sunburst and Star Light without relying on flashbacks. The episode exposes their past while they are focusing on the present which reinforces the fact that their backstories were left incomplete up to this episode.

The Parent Map intends to solve those holes that the staff set up with both Star Light and Sunburst in the Cutie Remark, especially Star Light. That single second which showed her room full of goth objects display that she was utterly depressed during her edgy phase before setting up Our Town in a desperate attempt in order to feel safe and fulfill her desire of being in a comfortable company. This puts the Cutie Remark in a better place than the first time it aired, acknowledging their backstories with this episode, but that won´t deny the fact that the transition of redemption felt really weird and somewhat sudden back in 2015 after destroying the destinies of other timelines. Considering that Star Light went really THAT extreme with those action, it was hard to emphasize with her at the time because the fans weren´t used to her antics and she was a potential psychopath for Equestria. Firelight might have been acting nicely in front of her just to prevent her from going full berserk and cause a mess because of her depression.

Sunburst´s case is less controversial because he didn´t adapt an insane route during his life yet one would question what the purpose of his character is and why he exists beyond being Star Light´s friend. The full contrast with Firelight and her daughter is that Stellar Flare like to look at the future for more plans. Sunburst however, didn´t achieve those intended plans when he had gone to Canterlot´s school and thus, while not a depressed pony, he embodies the concept of failure and disappointment (that´s why he didn´t believe his "important wizard" title when he was called back for The Crystalling, his convictions were hidden and kept in secret all this time)