Ref: Stator Vane
Just because you have not come across a problem does not mean that it is not valid. The fleet in question was the B747 classic during the eighties whilst being operated in the Far East envirnoment where the ground level humidity was very high. The procedure was dropped because of this problem and didn`t occur with the scanner operating. As an aside to this, excessive water comtamination collecting on the walls of large empty fuel tanks in this area of the world is also a well known problem.