Other drink makers are not allowed to make the exact same bottle shape. But you can still make a bottle. And you can still make a bottle that is very similar to the Coke design. But it can't be nearly identical. Translate that to Apple's home screen and that's what we are talking about.
What you are saying is tantamount to asserting that this work should have little to no protection, and be freely copyable once a design is made public.
Trade dress not about any single design choice but the combination of dozens of design choices which, when combined together, become an aesthetic trademark. And importantly, Apple spent millions of dollars on marketing to promote the fact that the iPhone looks a certain way and operates in a certain way.
The issue is that Samsung cloned this aesthetic in detail for the express purpose of hijacking Apple's existing media goodwill and advertising spend. And it also dilutes the value of Apple's brand.
Like they were in the UK? And forced to publish an apology?
What Apple patented was their design for a grid of icons. You could have created your own just like Google and many others did.
What you couldn't do was blatantly rip off their design which Samsung did.