Not only that, wouldn't he be the first player ever to have won at least 5 titles at each of three Grand Slams? AO, USO and Wimby
That's quite obvious, isn't it? No one else has won 15 slams. You can't really compare Laver's total "slam" numbers (amateur + pro + open) to Open Era players.
Besides, he already has the record at 3x4.