Hey, I say that if an Archdruid can be level 4, a level 1 can wander the planes.
Just kidding, you're right, it's one of the inherent silly things about fictional settings and the attempt to tie them to level systems without thinking too much about the incongruences.
Not to derail the tread but I'd also take the chance to point to Larian that:
1- Not every NPC we meet has to be necessarily in our level range, especially if the plot suggests he/she should be a power house by our standards.
It's nice that you leave us the option to attack and kill anyone in the game, but being free to try doesn't mean we should be able to do it.
2- ..And as we are on topic, I don't think we really need to SEE the level of every NPC stated under his name to begin with.