Geekbench is not just intended to be used to benchmark consumer systems, it is intended to be used by consumers to benchmark their systems and to have its scores interpreted by consumers. For that audience, the most important thing that a multi-core score needs to do is counteract the naive assumption that a 20-core CPU will be twice as fast as a 10-core CPU. Having one of the top-line scores be a perfectly-scaling multi-core score that you know will be widely misinterpreted by your audience and used by vendors to mislead consumers would be serious benchmarking malpractice.