He didn't? Remember, he thought he'd sent Vaarsuvius to the Demiplane of Extremely Painful Torture.
And absolutely no reason to do so. Nale is obsessed with being Elan's evil twin. He is not obsessed with following some optimization template.
Everyone has either levels or racial hit dice, and kobolds don't have racial hit dice. Whatever form of kobold has wings might, but while I look askance at people who suggest that Tarquin's secretary is too important a job not to be a high-level adventurer, I also look askance as the suggestion that Tarquin would choose someone completely unskilled for it. Most likely Kilkil is a decently leveled Expert.