I will not debate whether the rule is without foundation. I will say that Air Canada is not the only airline to have such a rule. I am not sure whether it is LH, AF, or both, but at least one of these two airlines has the same rule. Since I am perfectly comfortable using the pad that is built into my laptop, I never worried about where I heard it, but it is included in the video safety presentation of at least one of these airlines (both of which I fly regularly).