Those two examples were demonstrating what happens when you don't have provable consensus. They weren't issues with the validity of the blockchain, but debates

Those two examples were demonstrating what happens when you don't have provable consensus. They weren't issues with the validity of the blockchain, but debates over changing the software itself. They're good examples of why centralized development of a decentralized protocol still opens up the software to attacks (though with the option of continuing the blockchain without the software change, as Ethereum Classic did for a while), and demonstrates why having a provable consensus mechanism is important.