When I first saw this song on youtube I assumed it was Jiro's Japanese VA singing in English phonetically, because it was a clip from the Japanese episode, and honestly that's what it sounded like to me (someone whose first langue was not English singing English lyrics). So I was kind of expecting Trina Nishimura to do the performance when we finally got the dub episode. I was disappointed that wasn't the case, but then through googling I realized they actually got an American singer to record the song for the Japanese episode for some reason. I guess it makes sense for Funimation to keep this version in the dub as well since it's a "guest voice" situation that's already in English, not to mention with covid it's probably quite a bit more challenging to do a musical recording without the benefit of a real studio's tools/feedback than it is to just do basic dialogue recording (and I don't have any idea how Trina's singing voice is in general).
I was trying to think back to instances of characters in anime doing a major singing performance in-story, and how often the song itself gets dubbed (at least for shows where singing isn't the main focus like idol animes). The only really memorable thing I remember was Caitlin Glass' amazing rendition of that Casshern Sins song. I also remember some old Ranma OVA had the whole female cast doing a song, and the dub cast performed it, but I don't remember it being that special. I'm sure there's others I'm forgetting, but I feel like it's something dubbers tend to skip and just let the Japanese version play, since it's often challenging I'm sure to come up with an English rendition that's both meaningful lyrically and fits the lip movements.
I generally don't like it when a character's singing voice is different from the dialogue voice, though it's easier to deal with in things like Disney musicals where the songs are essentially a non-diegetic element. But it's different for something like this, where the song itself and her performance are in-story elements. As a viewer it takes me out of the story when the character's voice suddenly sounds dramatically different during what's usually an important moment that's been built up to (which was definitely the case here). And especially when music/singing is already a major part of an established character, you're introducing a not insignificant amount of diegetic dissonance that's hard to ignore. When they intercut between the song and Jiro having an emotional moment with her parents, it's supposed to show how the performance helps Jiro to reconcile her conflict between her love of music and being a hero, and her fear of disappointing her parents. But the effect is partially lost when she sounds like a different person during her big moment. Especially when you have a talented, well-established VA who has made the role their own.
