Happened to my wife's expedition. It has intermittent mis and the oem cat went bad. Replaced it and some time later the cel for "bad cat" cane back on. Same one that had already been replaced.
Yup. Misfire causes raw fuel to go straight into the converter, which has an effective operating temperature of well over 400°F. When the fuel gets in there it combusts and if allowed to go on long enough basically nukes the cat.
2001 GT Convertible /1967 Coupe
All the usual bolt-on's /200 I6, C4
And a few Explorers too... 2008 4.0 XLT 4x2, 1996 XLT 5.0 4x2, 2003 Sport Trac XLT 4.0 4x4