Amazon actually doesn't run the same Redis as the rest of us, I wouldn't be surprised if they re-wrote a lot of parts of it. They probably re-wrote the storage engine ect ...
The fact that they've done this for multiple other products built on FOSS projects is a pretty good indicator it can happen.
Aurora is a good example that's explicitly marketed that it's a different core storage engine, but they definitely make many modifications to the projects they're building on top of, but what kinds of changes really varies.
