Agree that several of the F. v. D. works ring true (the "Begebenheiten" concerning 4e, 7e and 12e Corps for instance), so PERHAPS (a guess) we are dealing with several publications that are Dressler's own work and several that he published/edited using tales from Guéhery? Especially as the one publication recounts the travels of the GQG to Silesia which Guéhery is said to have accompanied. How Guéhery ended up as part of N's suite/GQG is a mystery(!), but would explain how the author heard all these "inside stories" from court and headquarters when Dressler at least seems to have been with the field army.
Again the source for Guéhery's travels is:
The "Grundrisz zur Geschichte der deutschen Dichtung" Bd. VI, pp. 457-8 (see link below) give Louis Amanley de Guehry (or Guéhery--also the spelling used by the BNF) as being born in Paris in 1779. He goes to Berlin (1799-1804), first as a teacher at the Royal Prussian Artillery School and then "als Adjutant." From 1804 he "privatisierte" in Dresden but was attached to N's GQG in 1813 and accompanied N to Silesia. The only publications attributed to him appear to be theatrical pieces such as "Die Kosaken."