You defeat your own argument. A judo black belt THAT SUBMITS his opponents obviously displays serious grappling skills to tap other black belts. SHOGUN DID NOT TAP OUT ANYONE, let alone any black belts. He did not tap little Nog nor did he tap out Arona. He decisioned little Nog and ALMOST got an omoplata on an injured Arona who had already fought once that night. One close submission does not make him a black belt. Does he deserve a black belt in kickboxing under the Chute Boxe system for KOing people? Yes. Does he deserve a BJJ black belt? I do not think he does.
The highest level of BJJ is to tap out other accomplished and recognised black belts and win the Mundials. To win in vale tudo means you are a good vale tudo fighter, not necessarily a good grappler. By your logic Matt Hughes should be a BJJ black belt because he has beat BJJ black belts in MMA, however if he were to compete in BJJ in a gi against the same people chances are he'd get choked out.