Yogurt is a great food, and there's no reason not to work it into OWL, but that lowcarbluxury article and what Bowden says is inaccurate. They're both quoting the GO diet that that's what's misleading.

You could subtract all those carbs IF - and only if - the yogurt was FULLY fermented. This is not the case with store bought yogurt. Fully fermented yogurt would be face-twistingly sour and probably pretty runny. See Doreen's post, The Truth About Carbs In Yogurt for details.

So go ahead and enjoy it, but I wouldn't assume 4 g carbs per cup.