The claim (https://www.nag.com/nagware/np/r71_doc/manual/compiler_2_4.html#OPTIONS) is that
The -C=alias option will produce a runtime error when it is detected that assignment to a dummy argument affects another dummy argument. At this release this is only detected for scalar dummy arguments.
I know NAG will welcome feedback on desirable features from paying customers. After 30-odd years of development, I have to assume that the demand for more alias detection just wasn’t there in sufficient quantity.