I was looking at notebooks and thinking I want a big screen but with the keyboard in the center. I want my hands write in front of me, but I don't want to look to one side. I 'know' apple do it that way. Then I found an HP that was almost like that but the F was more left than the J was right, which are the home keys, so I thought still no good. Then I looked at the Apple and it was the same the F was more left that J was right. So I decided it must be right to do that, because Apple know best.
Yes, it's a "No True Scotsman variation" that takes into account the fact that a particular company gives TONS of attention to detail, builds lots of internal prototypes, and values usability and good industrial design ("how it works") greatly.
The fact that you don't know if something specific happened does not mean that you cannot reason about the high possibility of it happening given the historical information you have available.
Given what we know about Apple, Ives et al, what exactly do you believe of the two:
1) Apple picked the dimensions at random or without thought
2) Apple studied to find the best compromise for the device's dimensions
Surely Apple would have done that on purpose!