"it's an odd choice and raises some questions about the direction they're going."
Presumably the direction is that they (both games) are horror games, of the sort where bad endings have you suffer forever.
Think of it this way, perhaps: (heavy spoilers, obviously)
There's this game, Pocket mIrror. 2016. In it, you are a girl who lives in what turns out to be a nightmare world, tormented by a demon. Why is this?
Because her mother (Elise, of LGTS fame) made a deal with a demon for fame and glory, sacrificing her true love interest to the demon (Rozenmarine, canonically) and selling the soul of her second child to the demon (which would be you, the protagonist of Pocket Mirror.)
In the canon ending, the PM protag gathers the pieces of her shattered personality, breaks out of the nightmare, and wakes up in an asylum. Her parents are dead, her brother is gone. But, she has Lebkuchen's pocket mirror, so it might protect her in the future, and there is some level of hope in the ending.
Okay. Then comes LGTS, the prequel. You play as the mother, Elise. What do you expect? The canon ending has it end up so that Pocket Mirror even happens.
Does the canon ending matter? You CAN subvert the ending, and marry your love interest (whichever one), and thus in the world you now created, Pocket Mirror never happens.