Did you actually call a reservations agent and ask for their help rebooking you and get told there would be a fare difference? In my experience, if the request seems logical/reasonable and is going to get you home, agents often apply latitude during these irrops-related situations to rebook you without applying a fare difference. The published travel waiver guidelines are often a minimum guaranteed standard, with better results often available if you ask.

It can be hit-or-miss, though. I got a very sharp, ultra-fast sCO phone agent once who insisted on recalculating and charging the approx. $4 fare difference to turn W->V when I changed travel that had been cancelled due to a horrific New England snowstorm and rebooked 2 weeks into the future.

This approach (first publish "we waive change fees" and then, later, publish "we waive change fees and fare differences" if things get as bad as predicted) has been a standard operating procedure for at least the past year.