SAS - it just means that there has never been degradation of the bevel gears resulting in an M'ARMS alert, which is quite reassuring since they are fairly important! The system obviously does work because the M'ARMS data viewed post the ditchings showed a rising trend and threshold exceedance some time before the shaft rupture.
The information to prevent the ditchings was available but as we know from the reports, unfortunately the data wasn't looked at and/or the thresholds weren't optimal, hence the ditchings.