I quote

For as we know, when Dumas took back his serialized texts to turn them into books, he took great care to correct the text and change any typographical errors, any inconsistencies, and any confusing sentences that had slipped by him when he wrote the first draft
(Editor's note, p 757)

Which is a far cry from changing the character about and adding complexity, of course. But it is also not the same as just recycling bad form. Then again, I still remember inconsistencies in The Three Musketeers (age of d'Artagnan, I think?) which were apparently never corrected, so I don't know. Serves me right for not being a Dumas scholar.