I'm certain that he is sure.
I also experienced this.
But only in a different way. I was playing as the Germans and was fighting a battle against the Gauls. I had one spearband with 2 silver chevrons, at the end of the battle they had gained 2 experience so it changed to 1 golden chevron.
Then I went back to the campaign map after the battle and instantly the golden chevron had changed into 3 silver chevrons. So they actually lost one experience.
How weird is that!