RPCS3 relies on strict data integrity. When the emulator loads a game, it often checks file headers to ensure the data matches the PlayStation Network (PSN) or disc database.
"highly compressed" in the world of RPCS3 (the PS3 emulator) can mean two very different things depending on who you ask. rpcs3 highly compressed games work
"Highly compressed" versions of PS3 games found on third-party sites are often unreliable or dangerous: RPCS3 relies on strict data integrity