The characteristic rustling sounds that some pipe-bags make usually indicates that there is a layer of refuse-bag beneath the cloth cover. That's often evidence of a maker's over-enthusiastic use of bag dressing which is effective in sealing the bag and soiling everything else in the vicinity.
Inevitably, the excessive dressing also reaches the reeds and particularly the chanter reed. This is bound to affect the effective density of the reed blades and perhaps their stiffness too. In any case it can't be doing any good and I do think a chanter reed loses some brightness when there is contamination.
What do others think?
Francis