Hmmmmm.
@Godwinson 's right that this should make us reconsider core beliefs.
The one I'm looking most askance at right now is the assumption that witches and magical girls are the same entity.
The main points that have supported this interpretation up till now are:
• Witches follow the thematic themes and beliefs of their originating magical girl incredibly closely.
• Witches have acted on the beliefs and desires of their originating magical girls on many occasions - Kirika, Kazumi, Hinata, etc.
• Sayaka speaks of having personally experienced Octavia's suffering in Rebellion.
• Homucifer, who is clearly Homura, is born from the witch Homulily.
I'm... not sure what it would even
mean for witches to not be the magical girl that created them. It massively shifts the metaphor of witching out as depression, for one thing.
Still, there is some potentially interesting PMAS exclusive evidence supporting the idea of the two as separate, beyond Homura being able to bring forth a duplicate soul: Namely, that duplicate witches
already exist.
We've encountered enough witches by now that at least some of them should have been "familiar-norm", instead of "first-generation".
And yet, we haven't seen
any distinguishing marks to differentiate familiar-born witches from ones spawned by magical girls succumbing to despair. Ergo, familiars have been putting together a
perfect replica of existing witches.
I've explained this away in the past by saying that maybe the familiars are just "patching together" a close enough soul out of many mundane souls, that the ideal of that magical girl's soul can manifest through the facsimile.
And, sure, maaaybe that's the case - you could even attribute the duplicate Grief Seeds that Homura creates to whatever metaphysical process makes duplicate Grief Seeds possible in general.
But I think that we need to consider the possibility that maybe a witch
isn't the same thing as the original magical girl. In which case,
dewitching isn't possible. The best we could do is the PMKM thing, where we create a new person from the ashes of the old.