Oh, I absolutely assumed it had to do with them both being French and the Duke having him some nationalist sensitivities. You should see Adam Zamoyski dragging August III in a similarly personal manner, it includes some of the most vicious attacks I've encountered on the part of a historian.

(You *will* see it, once I'm ready to do my write-up on August III, but I'm still trying to get my hands on a copy of his most recent biography.)