Pet dealer psychologically abyused the hell out of this Sanae and gave her a Platinum badge, hoping some idiot would come along and not notice her huge anxiety problem.
People expect a smart sanae because it's a rare type. So he forces the training into her. If not then buyers would realize they're as worthless as common types and abandon them and value would go down.
Realistically they're rare because there's fewer of them and not rare because they have better quality. Fandom meta seems to theorize there's a bucket of intelligence to go around and the more there are the dumber the yukkuri becomes.
*Tremble...**Tremble**Tremble*Long time no seeSoldYuwaa~~
Shanae that looksh like Shanae!Yua...YU!!*Clench♡**Drip*Yu...