This is about the visual aspect. The accusation is that Samsung deliberately mimicked the look of the iPhone at the time in a bid to cynically confuse consumers

This is about the visual aspect. The accusation is that Samsung deliberately mimicked the look of the iPhone at the time in a bid to cynically confuse consumers at point of sale. That they changed the interface of the OS too is a smoking gun. It's like copying someones homework, but just swapping a few key words and sentences and claiming the work was entirely your own. I agree the question should be asked, I don't necessarily agree with the way Apple chose to ask it, but that is neither here nor there. They feel aggrieved, they are legally entitled to pursue this how they see fit. The "its just a rounded rectangle" argument is reductio ad absurdum.