Apple love to preach "the UI gets out of the way of your content" with each new redesign, but how true is that in practice? Let's compare the total height of the Safari UI with a toolbar, favourites bar and tab bar visible, across the three latest Mac OS design languages – Yosemite, Big Sur and now Tahoe. I've added a red line for emphasis.

It sure looks to me like the UI is eating more into my content with each redesign.

@tuomas_h I'll keep saying this is the preparation for a future touch friendly macOS
@lasombra_br People made this exact argument when the previous redesign (Big Sur) was unveiled and it turned out to be a nothingburger. I’ll believe it when I see it. Until then this is nothing more than reduction of information density for no obvious benefit.

@tuomas_h I'm not saying it's going to happen today or tomorrow, but there's no other obvious explanation, to me, to justify this amount of padding.

As you said, we'll have to see it to believe it.