It also 'starts off better' because they refined its components throughout the rest of their ecosystem over the last half decade (or more?). If you look at a variety of unprovoked UI changes in iOS and tvOS, or hardware changes in iDevices, they now look like field tests at scale for learning, before bringing together these new, now proven, things.

It's a way of development seen almost nowhere else.

Or I'm giving them too much credit ... but I don't think so. I think it's evident they seeded hard parts throughout the rest to learn at massive scale.