^^ If you buy a $100.000 A8, you don't want it to look exactly like a $40.000 A4!!
It's great to have a "family spirit".
But having every single car look exactly the same as the others bar the rear lights... Having every new car look almost exactly like the previous one... Knowing how a car will look like before the first pics leak... That is boring, and absolutely not a good thing for me.
Audi is copy-pasting its design, and it's really too much (or, better said, too weak an effort).
Concerning the flagship: you won't tell me an A4 is a better flagship than an A8, will you? Technology, comfort, finish and materials, inside space, fancy gadgets and exepensive gimmicks are not on the A4 side.
And I'm sorry, but having a spacious car where the front passengers have enough space and armrest, rear passengers don't touch the roof or the front seats, where your seats are twice as large as in a normal car, is a much better experience than sitting on each other's knees by lack of space. Therefore, the A8 is the flagship and the A4 isn't.
Absolutely nothing speaks for the A4, and the flagship is NECESSARILY the bigger car (unless you're going to Lotus or Ferrari).