He is mistaken, but for different reasons. BU is a unilateral split. If, after BU pulls the trigger on their hard fork, the Core chain ever overtakes the BU chain, all BU coins will be permanently destroyed and all transactions involving them will be forever invalid. Mass panic will ensue and their altcoin will be worthless. That's why Core devs are begging BU to make their fork bilateral, but they won't listen (or they pretend not to listen because they don't have the competence to implement a bilateral fork).