Is there anything about the performance on unknown files? I've tried a few that aren't "basic" but are widely used enough to be well supported in libmagic and

Is there anything about the performance on unknown files? I've tried a few that aren't "basic" but are widely used enough to be well supported in libmagic and it thinks they're zip files. I know enough about the underlying formats to know they're not using zip as a container under-the-hood.