Really? What versions of KSS did that? I don't recall ever running into it, and I started with KSS 2.x on KRC1s. Whenever I failed to DECL a variable, the controller would invariably fail at compile time.
I can test on the KRC2 to make sure it lets me use variables that are not declared. That bot is in production right now, but I can run a test when it is down and let you know the KSS that it is using.