There are definitely a few things it does that are weird, and this article hits on a few of them.
But, I'll call special attention to the whole "adaptive padding thing" as a broader signal for something I feel that SwiftUI does very, very right and more UI frameworks need to start thinking about. Its made to design iOS apps. iOS has a design language that (1) is relatively consistent, (2) changes over time, and (3) changes across the many devices Apple supports.
In this era of many, many devices (don't just think Apple here; think any device; think VR, think TVs, etc), we need to operate at a higher layer of abstraction than most UI systems operate at. Most websites are pure garbage on 35" ultra-ultra-wide displays. It took a decade before mobile web entered the "generally useable" state it is in today. Ever tried to enable an ultra-high DPI setting on, say, Ubuntu or Windows?
All of these are getting better, but they only get better because the underlying technologies are becoming more generic.
> If I forgot to put padding between HStack elements, well, shame on me, there should be no padding! All mistakes are mine.
Wrong, and Apple has the data to prove it. When you release a poorly designed app to the App Store, the mistake is your's; your customers suffer because of it; and, it hurts the optics of application quality on the App Store, and thus Apple suffers.
This is relatively easy to draw a comparison to, say, manual memory management in C++. "If I forgot to properly bounds check a memory segment, well, shame on me, there should be no bounds checking! All mistakes are mine". Sure; and now your customers are vulnerable to hackers. You have a higher responsibility than just your Pride.
The defaults should be Safe. There should be options to override them when I feel confident I know what I'm doing (and SwiftUI has this, not the least of which being, you don't have to use SwiftUI, you can mix-and-match SwiftUI components with traditional iOS components).