Thus if you claim it is not solvable, then you have either found an error in their proof, or you have redefined the problem in your own way. I suspect the latter.
As with all such systems, fault tolerance is achieved up to a specified number of faults, and no farther.
If messages of the generals can't be faked then even 99 of 100 traitors is not a problem. I think he didn't redefine the problem, more likely he just forgot to provide some details.
EDIT:
From that paper:
With unforgeable written messages, the problem is solvable for any number of generals and possible traitors.