It's not modifying the generator. The generator may be a proprietary black box. It's wrapping the generator in a bash script that pipes the result through AWK, etc.
However, if your awk script requires the current state of the generated code as input in addition to the output of the black-box generator, and tries to reconcile a diff between the two things, then yep, I consider that busted.
Which is itself a generator
Since the issue is the maintenance of such systems, it is absolutely relevant.