So, Gnome's design and Apple's didn't exist in a vacuum. I'm not saying Apple told someone to go rip off Gnome 3, or that Gnome 3 is just better than Big Sur in some way. But I think it's altogether too harsh to deny it had any influence when we look at the changes from Catalina to Big Sur.
Anyway, here is gnome 3:
https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2F...
here is big sur:
https://cdn.osxdaily.com/wp-content/uploads/2020/06/macos-bi...
Let's take a look at one of the most shown off redesigned apps
Here is Mail.app (sierra to catalina):
https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2F...
Here is Mail.app (Big Sur):
https://i1.wp.com/morrick.me/wp-content/uploads/2020/08/defa...
Here is Gnome's mail app (predates big sur by several years, even in this incarnation):
https://wiki.gnome.org/Apps/Geary?action=AttachFile&do=get&t...
So, Gnome's design and Apple's didn't exist in a vacuum. I'm not saying Apple told someone to go rip off Gnome 3, or that Gnome 3 is just better than Big Sur in some way. But I think it's altogether too harsh to deny it had any influence when we look at the changes from Catalina to Big Sur.