I thought this thread had died. I haven't found the order referred to, though I have bought myself both volumes of Lecestre in pdf and read through them. My feeling is that the area was pretty thoroughly stripped but that the devastation was most likely incidental.
I gather you haven't found the source for the idea that Napoleon had refused to devastate the country either. However it could be from Odeleben again vol 2 p 42-43
"Napoléon lui-même ne croyait pas avoir fait une aussi grande perte à Leipsick. Peut-être lui a-t-on caché la vérité,comme à l'ordinaire; car comme on savait qu'il répugnait à entendre parler d'une grande perte, c'était lui être agréable que de lui faire de faux rapports.
Il dit lui-même, quelques jours après: « J'aurais pu sauver six mille hommes, si j'avais brûlé les faubourgs de la ville; c'était le droit de la guerre; mais je n'ai pas voulu le faire. »"
If so, it would appear this is just Napoleon making excuses - even assuming Odeleben can be relied on. According to the latter there had been fires breaking out in the faubourgs anyway.
With respect to the translation, though the translator (1817) was at pains to explain that he had replaced 'l'Empereur' by 'Napoleon' or 'Bonaparte', his comments at the end are more critical of Odeleben than anything. He seems to resent particularly aspersions against the honour of the French army - of which there are quite a few.