The issue with this narrative is that the "they" isn't the creators, it's the network. The Ethereum core devs can do whatever they want, but if nodes don't migrate across the hard fork then nothing happens.

The code is the contract, enforced by a decentralized network of actors. Of course that network can at any point change the contract if the majority of them agree to do so – how else would it work? The key is that there is no way for individual actors to modify contracts at will – you need consensus. It's the difference between oligarchy and democracy.