I realize this is contrary to "be conservative in what you do, be liberal in what you accept from others", but I never thought that was a good way to write software.
But if the choice, after a Redis update, is between:
a) my software breaking and, hopefully, an error message saying "redis failure parsing 'XYZ'"
b) my software /maybe/ continuing to function, while passing commands to Redis that it's ignoring
I would always pick (a), and I think most programmers would think likewise.
Now the cache server has a security update, so you apply it right away. But now when it gets your invalid command it not only returns an error but it drops the connection. Your client doesn't handle this well, and now your caching is fully broken and your server falls over from the load.