I have no quarrel with the assertion that computing is one of if not the single most important field to learn in modern society; what I am suspicious of is that there's any long-term performance benefit of making children learn "pre-computing" through iPad apps at an age where they're not ready to learn real computing.

Of course if a particular child shows great initiative and engagement with pre-computing, they'll do well with real computing, but then why not just start with computing? For the ones that don't care, why not let them continue reading books they enjoy and playing outside?

That's how American children learn to read and write. It's not how Russian children used to learn to read and write; they started school much later, and immediately began fairly mature studies of classic Russian literature and poetry (Pushkin, for example).