He could easily mine to a burn address like 1111111111111111111114oLvT2 or 1BitcoinEaterAddressDontSendf59kuE and we knew that these coins won't be used anymore.
No reason to dictate what he should do with his coins, to burn them or not. He is free to use the coins as and when he likes, the fact that it hasn't moved yet doesn't necessarily means that he intends for it to be burned regardless.