Not sure. Does take skill to keep the boat moving under sail when the wind is very light.
Reminds me of an inland river dinghy sailing club I used to belong to. The stretch of river was sheltered by a bowl of hills, so unless the wind was really strong (when it was horribly turbulent and unpredictable) it was usually very light. Summer mid-week evening races in particular took a lot of patience and skill. Not unusually you'd have to hug the shore and only have a slight air from the heat rising off the bank to sail by. Going upstream in such conditions it might take 10 minutes to pass an angler (they'd show their displeasure by chucking bait at us). There was an informal club motto 'Any fool can sail with wind....', and there were two alternative endings, according to taste.
I think that in order for anyone to be called "skilled" they would have to have amassed a fair degree of experience. For a sailor it would generally be assumed that some of that experience was in rough weather and big seas. So I'd say it's true.