Thank you for the replies! I just took a look into the manual, and there I found the "magnificient" line stating what we experienced, too: "Fon non-player character paladins, this bonus is fixed." From a roleplaying perspective, this takes so much fun out of strictly behaving in a certain manner - 'no matter what'.
On the other hand, this keeps us from bringing too many paladins upfront, right? So far, even bringing two really gave me the upper hand in the first harder encounters.