"The correct procedure on finding damage would therefore be for a concession to be sought
I hope he (AMM) read (received a good brief on) the maintenance schedules before he wrote that. Finding damage can only occur if the tradesman is scheduled to examine the component. We cannot rely on the men choosing where to look for damage. We have maintenance schedules to meet that specific need.
However, we know from a previous Flight Safety Report that there is no maintenance policy for the SCP ducts, so I guess there is no examination policy for the insulation either, but I'm just guessing.