Why is everyone under the impression that Michele Knotz is guaranteed to voice Misty? Knotz only voiced her once, and that was in The Mastermind of Mirage Pokémon. It was such a one-off thing, so I have no idea why The Pokémon Company would rather let someone who voiced her only once over six years ago do the dubbing instead of letting Rachael Lillis, someone who is a lot more attatched to the character, reprise her role as Misty. If Giovanni and Gary can keep their 4Kids actors, then I don't see why Misty can't keep her actor, too.
Considering the amount of trouble they would have to go through to contact Rachel Lilis to do what...maybe 3-4 lines at the most....would it be worth the effort in their perspective?
Misty probably won't be on-screen in the flashback for more than 30 seconds. They're only showing a brief clip of Charmander in the rain and then moving on to other stuff like the Koga and Blaine Gym matches and so forth.
And the difference is Gary and Giovanni had full episodes and major roles when they appeared. Misty's character is not truly appearing in an episode, she's getting a brief scene in a Charmander flashback that will probably be extremely brief.