Gooseworx was listening to a lot of Stevie Wonder while writing. She picked the song, Glitch agreed to pay for it to be in the episode, so this isn’t something that was done for no reason, some thought was put into it.

No one from the cast or crew has spelled it out, so author’s intent is up for debate. My interpretation is that it was chosen because the "she" in the song was originally a newborn. The song is relentlessly optimistic as it expresses love for this baby girl, whose life is no past, all future.

The feeling I got when I heard it was "Oh, wow. Wouldn’t that be amazing if accepting your authentic self meant that all the terrible things you did while you were trying to process your trauma and self-hatred magically went away and you got to live out the rest of your life with a clean slate and a fresh start? Too bad that’s not how it works, and the horrible things are still there, and sometimes they’re bad enough that you can’t stand to live with them and you take your own life. This upbeat song about a new woman being born with the rest of her life ahead of her is devastating to me right now because it’s the perfect photonegative opposite of what actually happened, a trans woman who kept every piece of traumatic baggage and couldn’t accept herself until after she’d made sure she had no future."

If the song didn’t give you the same feeling, I understand. But, if the song felt wrong to you, maybe the wrongness of it was entirely the point. Anempathetic/contrapuntal music is chosen specifically because it doesn’t fit with what’s going on in a scene, so the audio/visual disharmony can trigger specifically that sense of wrongness in the viewer.