> Why do you think the standard iPhones only does USB 2.0 transfer speed?

Because they saved die space in silicon? Same reason the MacBook Neo only has a single USB 3 and a USB 2. It seems that their A-series Pro silicon only has hardware for a single USB 3, and their non-Pro silicon doesn't even have it at all. I highly doubt they are sparing pins from the connector, the complexity of making a special port variant for that far surely outweighs any potential savings.