I'm a little confused by this take, because I'm not sure what lesson Alphinaud is supposed to be "learning" he's consistestly been a person who tries to use diplomacy and rhetoric to convince people to help each other or cooperate.
In ARR his arrogance led him to surrounding himself with yes-men who flattered and manipulated him while they plotted the bloody banquent, and HW has his dealing with self-pity for that incident. But it's not like he was supposed to learn that using diplomacy and rhetoric was a bad thing, so of course he goes back to trying it in ShB and EW. He's remained confident and steadfast in his values, but I don't really see him as arrogant anymore.