// For `CollectiveReduceV2Op` we have 3 cases:
// 1) `is_stateless` is true turns off automatic ordering and we purely rely on
//    instance_key to distinguish collective groups. In this case, ordering
//    tokens are irrelevant. Each collective group should have a unique
//    instance_key at runtime.
// 2) If at least one ordering token is present, then we purely rely on ordering