The article doesn't contain the term 'Safari-tab'. It does have 'Safari-like tabs' in it, by which I would imagine they mean tabs, like you get in the Safari user interface.
what happens if the app already have tabs inside? Like sublime for example
I don't know any more than you, mate.
They meant all apps made by Apple, not random apps, as far as I could tell.
I could be wrong but I think he said all apps without any developer changes..
It's not only Apple apps.
I’ve been asking for this for awhile now. It has never made sense for every app to try to tab-ify its windows in a slightly different way, when it so clearly needed to be a window manager feature. Although, I really hope it allows inter-app interleaving of tabs, and not just all-one-app tab stacks.