>>33175501>Being given the title.Who said she was given the title? It would be more in character for her to have given herself that title, what with how she boasts how cute she is when giving attract. Also, while Miltank certainly is That One boss, in universe, she's no more renowned than any other Gym Leader. Compare her only saying "I'm warning you-I'm good!" and being picked at a young age to be a gym leader with Bugsy's opener, the leader before her who is presumably about as young as she is.
"I'm Bugsy! I never lose when it comes to bug Pokémon. My research is going to make me the authority on bug Pokémon! Let me demonstrate what I've learned from my studies."
And also Falkner, who has a birthright to being Gym Leader from his father.
"I'm Falkner, the Violet Pokémon Gym leader! People say you can clip flying-type Pokémon's wings with a jolt of electricity... I won't allow such insults to bird Pokémon! I'll show you the real power of the magnificent bird Pokémon!"
Neither one seems to have more or less prestige in-universe, and both certainly have reason to think highly of themselves, with Falkner's birthright and Bugsy being undefeated regarding Bug pokemon and a foremost researcher. Yet neither acts the way Whitney does.
Claire's is based on a narrow-minded viewpoint of someone who has been relatively secluded in the mountains combined with being a Dragon user related to the Champion of the region. It's multi-faceted, and not just based on something like being a young Gym Leader.