Thanks for all the replies & links.
Although the Saxons aren't mentioned as reinforcements they are also not explicitly excluded, although reinforcements are only mentioned for 4th & 12th corps and so it's unlikely that the Saxons gain some even if they should have it easy in their own country to reinforce their troops.

Now I don't want to derail my own thread but the quote of "Geschichte der Sächsischen Armee in Wort und Bild" that mentions the Poles were left behind seems wrong, at least I hope so.
AFAIk the Polish division likely didn't participated as a divisional formation but its elements seem to have been at Dennewitz, at least the Polish Uhlans are mentioned often. And one of the foot regiments seems to have been attached to the 32nd division what leaves the other foot regiment(with 2 bat.) as only contend of the Polish 27th division. That might explain why the division usually doesn't show up on any map.
To leave the best troops behind at Wittenberg seems pointless anyway. Wittenberg had a garrison so was there any need to leave additional forces behind, especially the best units?