I just did an image search for "classic macos" and one of the first hits was from https://www.versionmuseum.com/history-of/classic-mac-os. Look at those System 1 screenshots, from 42(!) years ago -- round corners on Puzzle and Calculator, square corners on Note Pad and Control Panel! No consistency at all, isn't it infuriating?
Article author here. I think the quoted claim is somewhat misleading. There are at least two different ways to interpret a UI feature as "not new":
1) The feature has been in the operating system all along.
2) Something analogous existed 40 years ago and then disappeared long ago.
You're referring to 2, not 1.
The only reason I chose Calculator app for my screenshot is that its window is very small, which allowed me to make a small screenshot, because people may be reading the blog post on small phone screens. In other ways, admittedly, Calculator is not a great example, because its window is not actually resizable, and thus it's not the type of window that you would normally place in the corners of your screen, like a resizable document window.
Rounded corners on a "widget" type of app are not as objectionable. As other commenters have noted, the calculator in "classic" Mac was a special Desk Accessory. In contrast, on Tahoe, the varying corner radii affect ordinary document-based apps.
Consider Mac OS X 10.0 Cheetah. The top of the windows had rounded corners, but the bottom did not! https://512pixels.net/wp-content/uploads/2018/08/10-0-Cheeta...
TextEdit, for example, did not start to have rounded bottom corners until Mac OS X 10.7 Lion, which was itself much maligned for bringing the iPhone UI to Mac.
You're right, what I had in mind was 2, although a bit more general; I think there have been similar kinds of inconsistency in the Mac UI since the beginning, in various forms, almost always intentional.
So I think it would be wrong simply to say "the UI has gone a cliff, they've just thrown away their own HMI guidelines." You can certainly dislike what they've done (and I do dislike it!) but they at least have a somewhat logical goal in mind -- in this case, making the corners neatly fit various different kinds of window content.
Having said all that, there are also some real bugs and unintentional glitches, like scroll bars and other widgets not fitting correctly. I'd agree that seems to be happening more often in recent years, so their quality control has gone downhill.
My own view is that Mac OS X 10.5 Leopard was the beginning of the end, and it's gone downhill ever since.
> they at least have a somewhat logical goal in mind -- in this case, making the corners neatly fit various different kinds of window content.
I would emphasize "somewhat", because as noted, the corners do not neatly fit the window content at the bottom, which is ironic, because Apple claims that their intention is to emphasize the content, but their implementation actually clips the content!
Some cool details here: https://en.wikipedia.org/wiki/Desk_accessory
Like Tahoe, it was deliberate and there's an explanation for the difference.
But I do wonder if people at the time felt the same way.
I particularly like this Bill Atkinson tidbit at the end:
Bill Atkinson complained to me that it was a mistake to allow users to specify their own desktop patterns, because it was harder to make a nice one than it looked, and led directly to ugly desktops. [...] So he made MacPaint allocate a window that was the size of the screen when it started up, and filled it with the standard 50% gray pattern, making his own desktop covering up the real one, thus protecting the poor users from their rash esthetic blunders, at least within the friendly confines of MacPaint.
(He was totally right, making your own desktop patterns was fun but the standard checkerbard was far and away the best choice.)