FWIW, to be honest I had autism spectrum disorders in mind, though I certainly don't equate autism with handicapped general intelligence. I intentionally avoided using the term autism (even though some of the best examples I had in mind come from studies on autism spectrum disorders) as it's such a very broad label with different etiologies and different constellations of traits. An autistic child with fragile X syndrome is likely to have many objectively identifiable and severe disabilities, whereas some other child with autism might have few or no disabilities, especially in a more diverse and accommodating society that isn't organized to punish people who don't easily fit into a mold. I wanted to point out that some seemingly desirable trait can actual reflect other, categorically undesirable traits. Such value judgments are especially tricky when label like autism are thrown into the mix, and in any event I wasn't keen to attempt to identify anything in particular as negative.
Back to my original point: there are many more ways for things to go wrong than for things to go right. Similarly, abnormal faculties often coincide with abnormal deficiencies--were it otherwise genetic evolution dictates it wouldn't be abnormal. That basic calculus means that when abnormalities emerge, all things being equal and long before we can know anything about how things will play out individually, it's not rational to be envious or given to feelings of inadequacy, which is precisely what we're doing, intentionally or unintentionally, when we're drawn to stories about precocious behavior.
It was eye opening to come to learn how my spouse as well as other people I've spoken with who have studied various aspects of child development have a very different perspective on abnormal and out-of-order milestone development. At the same time, these are the people least likely to construe debilitating abnormalities in the same negative light as wider society. But they understand 1) the cold, hard calculus and 2) that any abnormality, whether widely construed as positive or negative in society, comes with a real, additional cost in time and attention, particularly for attentive parents who wish to ease their child's transition to independence given the harsh realities of the world. Simply recognizing and internalizing differences so as to avoid confusion later on in life is a real burden on everybody involved.