The gearbox
casing was damaged, cracked with pieces missing even. As was confirmed by Ferrari on the Italian coverage live on air in Japan(and also SkyF1's Ted Kravitz in that video link above @3:35sec).
But the complicated FiA rules only take into consideration the gearbox
cassette. As was explained by Charlie in that video link I posted. It's a very technical situation that maybe Ferrari has an advantage with the design of their so called "gearbox".
Where as maybe with some of the other teams gearbox designs, if they find only the gearbox casing is cracked, the entire gearbox unit has to be changed as it is linked with items or some other reason??
Or.., maybe, just maybe the FiA were (desperately) doing their best to keep the championship alive?? It's not like they have not done it before now is it? They have form twisting the rules when it suits their own objectives.