I gave you several examples of things Apple could have just not even had bothered with because they are minor and somehow you read the only additional difference is the spacing between icons? I ran the numbers. I did the math. I showed that Apple doesn't act sloppy with the UI and proved that the iPad is not just a large iPod Touch.
So it's dumb for them to spend time on a unique UI for a different size device YET THAT IS EXACTLY WHAT THEY DID WITH THE iPAD. They uses iOS and they used CocoaTouch, but the UI is completely redesigned for the 9.7" 4:3 display.
Back to icons: if made no sense economically to idealize the UI for the device THEN WHY DID they alter them? As I pointed out they are clearly different pixel sizes. Developers have to include 3 different icon sizes today with Universal apps and on Wednesday it will be 4. So again, if they would never do it then why did they do it? The answer is in the proof. The iPad is only tablet worth getting because it's the only one that thought about the user experience.
Do they both use the same processor - yes or no?
Do they both use the same operating system - yes or no?
Is the UI optimised for the respective screen size - yes or no?
Apple could make a 25" iPad and it would basically be the same. The ONLY difference is that the UI is optimised for the screen size. That is because the the OS is not capable of scaling itself to match the screen size. That's why you have to buy the same app twice if you want it on your iPod and iPad.
That however does not make them fundamentally different products in the same way that an iPad and a MacBook are different products.