Southwestgabe's response to the flat-tire rule question when the no-show policy was announced was :
Customer Service Agents will work with Customers on a case-by-case basis if they miss a flight due arriving late to the airport.
Which means, basically, that you shouldn't take for granted the flat-tire rule anymore.
Hopefully GA's have been trained that the no-show policy shouldn't be applied in cases where circumstances outside the pax control cause them to miss the flight, and they are at the airport within two hours of original departure time. But I suspect it's all up to the GA's discretion, ultimately. <rolls eyes>