The article says that studies which controlled against dance or sports showed no additional effect. Which looks really good for music IMO- because exercise has incredible benefits.
Maybe as compared to sports, music doesn't show additional benefit- how about as compared to watching YouTube videos? Playing flappy bird?
I find it hard to believe that we can really 'prove' anything with respect to child development. The studies have a phenomenally low lack of control on one end, which produces a LOT of noise. On the other end- we have no effective ways of measuring child development. Standardized tests or IQ produce metrics that are somewhat useful to measure how productive a child may be, but is that really what you want to optimize for as a parent?
What we really want to do for our kids is optimize for lifelong happiness. And we aren't even remotely close to measuring that.