I was thinking the same from the root of this argument: "redundant encoding" isn't a way to automatically fix errors, but rather only a way to detect errors. Like a one-bit Error Correcting Code: the fact that the parity bit is wrong tells you something is corrupt, but it doesn't let you know what the right value should be. There's one useful thing you can avoid doing in response to such an error being detected: not rely blindly on either the implementation or the specification being correct, but instead check them both.
In fact, I was reading about the bitcoin redemption vulnerability in stripe, and how often times security bugs are discovered by "huh, that's weird" rather than by eureka, and this ECC (error correcting code, see the pun?) seems like it would help to provoke that, and likely validates the amount of effort that it takes.
