Perhaps they did not know....thus why would their "Ticket" be in jeopardy?
If you sign for the aircraft and spank it in following a performance chart that the mass of the aircraft exceeds - whether it is an engineering snafu or just not checking the C of G and Mass properly - it's still going to be the pilots fault.
Fortunately - and it seems so in this case, the error was noticed (sometime later) and the only red faces are the engineers who got their sums wrong. I have challenged weight and balance sheets before when thing didn't look quite right as I am sure many here have.