"Brandon says that he fought well and he will be ready once Ash and his Pokémon learn to fight as one."
Is this even a thing? What did Ash's Kanto starters have to do with this? Or were they just stalling for the release of Diamond & Pearl.
what Brandon meant was Ash's Pokemon had to learn to fight as one team, not as individual Pokemon and that would make them stronger.
I think he means that Ash should believe in his newer Pokémon and not use them as a tool. Pokémon should be his best friends and not a tool he use for battling.