Because TIB is a proprietary format, you cannot simply rename the extension. You need a two-step process:
When you convert TIB to ISO extra quality, you are not just changing a container. You are asking the software to:
A "low quality" conversion results in an ISO that mounts but refuses to boot, or one that loses file permissions, partition structure, or critical system reserved areas.
Result: A bootable ISO, but no quality gain. The ISO will be larger (no compression) and lose all incremental backup features.