Yea, that makes sense. As an American, I think if someone showed me anything that's supposed to be in a pair then I would talk about the singular item in the plural, even though that's technically wrong. I translated this sentence as "These skis are made of wood" because my mind always thinks of skis as a pair and thus plural. Same thing with gloves, shoes, cigarettes, speakers, etc. If you showed me one, I'd describe it in the plural because I know there are more than the one being shown.