User blog comment:SilentShadow87/The Underrated Tornadoes of the Enhanced Fujita Scale - pt. 1/@comment-26074320-20170201100310/@comment-26074320-20170201115741

Yes, the Philidephia tornado wasnt rated the now traditional way. The EF5 rating was indeed granted partially because of the very deep ground scouring, amongst other things. For example, several manhole covers were removed from the ground, a clear EF5 indicator, yet the tornado only caused mid to high end EF4 building damage during its time on the ground, so the EF5 rating is heavily disputed as a result.