Something is not right here.
Pokémon - Sapphire Version (GBA)(U)(v1.0) can not be trimmed.
Not sure about Sapphire, but if games don't have any or much garbage data, then there really isn't anything to trim. Some games do take up the entire ROM. That's not that uncommon with GBA games. If a ROM doesn't have anything to trim, it will just say it has already been trimmed.