Ardiane is Cas, but I wouldn't call that a mistake. It's entirely possible IC that Ardaine (sitting on the horse) and Ilisandoral (the elven loremaster in the carriage) could be seen as different people. They might be the same changeling, but that's not evident to people.

Ilisandoral - Grumpy elf 'hiding' in his carriage.
Ardiane - Pretty half-elf sitting playing the flute
Cas - Both of the above and separate.