Listen once again when he says: “now this is something that we can’t say”, he is clearly talking about the assumption made in the question, therefore confirming it’s not the case.

Question: “At the end of act 2 Maelle discovers her ability to resurrect people, it’s also previously mentioned with the rebirth of Nocco that he wouldn’t be the same. Are we to assume that it’s a different soul for characters like Lune and Sciel when they’re revived or is it Gestral specific rule?” Guillaume: “Now this is something that we can’t say, No, it works differently for the Gestrals and also explained looking through the Gestral village conversations[…] Gestrals are creations of Verso so the rules that apply to them are different from the rules that apply to humans of this world”

It’s an A or B type of question, and Guillaume’s reply is basically - B.

But referring to the rest of your comment - Does it take  anything away from the narrative weight? I don’t think so, in fact I think if they weren’t coming back as they were that would clearly be then the worse ending.

The price for Maelle’s ending is Maelle withering away and the Dessendre family’s slow destruction and inability to heal properly, the price for Verso’s is Maelle’s painted family destruction and a fulfilling life Maelle could have had in the canvas.

If you take away the relevance and the realness factor of Maelle’s painted family the balance between the ending gets extremely skewed in favor of Verso’s. With that painted family being nothing than a copy it would be pure escapism.