I read it as him agreeing with your two "you can't" statements.How is it false confidence? I never said you could ALWAYS pull it off on someone, but a BJJ blue belt who can consistently nail their fat, muscular, skinny, short, tall, aggressive, sneaky, gi, or nogi classmates with a Kimura setup has a very good chance of being able to pull it off on someone who is untrained.
The biter? Not so much.