It has meaning. By looking at a table in e.g. getopt() call and an output of --help I can often infer modes of a program that I probably need, to do my job when someone asks me to. Whether this getopt() gets called or if a program does what it claims in usage() is not my concern. I was commanded to guess the usage and I do it without burying into the halting problem. And so does that hypothetical AI.

Decidable or undecidable is about maths, not practice.