That does seem to track, the USUM entries also solely focus on the type of flower rather than the origin of the floette specificallyThe XY lore in this thread is a little mistaken — AZ’s Floette wasn’t a one-off, accidental creation. Watch the war flashback again — it exists as an Eternal Flower Floette before it dies in the war. It’s even using Light of Ruin in the big splash image. The only thing the weapon did to it was render it inmortal.
According to Masuda, that Floette was given to AZ as a gift from his mother. She must have gotten it from somewhere, so I think there’s plenty of wiggle room to say that others could have existed, especially since in ORAS, an Eternal Flower blooms next to the big tree in Sootopolis after Groudon/Kyogre is defeated. Personally, I always assumed EF Floette is just what happened when a Flabébé or Floette bonded with that species of flower.
Kalos revisit flower lore gonna be nutty!