I agree that the described bug is a very frustrating bug. As for old squares vs the new circles, that's an aesthetic choice I'm sure some will like and some won't. My impression is that the old UI is more in keeping with the HP calculator it emulated. Personally it's not something I'm overly concerned about but I can understand how some may be. (Don't get me started on the Contacts icon which I can never seem to be able to find.)
> "and had a larger touch area"
Your comment regarding touch area made me curious. While the button image area is smaller, in my very simple and admittedly limited tests I seem to be able to activate the button with touching the button only tangentially. Even with my pinky I can't not activate a button when attempting to avoid them by pressing in the space between them. This leads me to believe either the active area extends beyond the button image area, or, more pragmatically, fingers are large enough that they're going to end up activating the buttons regardless. Would you mind going into more detail in how you determined that the touch area is reduced in the iOS 11 calculator?
I look at a button as defined by its shape as "perceived touchable area".
A circle enclosed in a square has a smaller area than the square enclosing the circle. You're seeing the new buttons as circles (thus smaller area), even though behind the scenes (as your little experiment has demonstrated) the buttons are still squares (real touchable area) on a grid.
I would also argue the eyes have a harder time parsing the layout, as the visual boundaries between the circular buttons have more complex shapes than the old UI, where the boundaries were very thin lines.
If you want to run another "experiment" – albeit theoretical – imagine we shrink the "perceived touchable area" of each button even further, say we get rid of the circular background and keep solely the digit displayed on the button. Your eyes will now perceive the visual representation of the button, as only the digit, and I would say our initial impulse is to touch what we see and not some imaginary boundary we know exists.
I see what you’re saying, but I don’t think at the end of the day this ends up mattering much, if at all. For example, when trying to press the buttons quickly to reproduce the bug, I didn’t feel the slightest need to be precise. Similarly, if the buttons were physical, I believe they’re large enough that people wouldn’t feel much (if any) need to be more precise due to the inherent “slop” buttons have. Though, if you have reference to UX tests that show otherwise, I’d be interested in reading it.
> "and had a larger touch area"
Your comment regarding touch area made me curious. While the button image area is smaller, in my very simple and admittedly limited tests I seem to be able to activate the button with touching the button only tangentially. Even with my pinky I can't not activate a button when attempting to avoid them by pressing in the space between them. This leads me to believe either the active area extends beyond the button image area, or, more pragmatically, fingers are large enough that they're going to end up activating the buttons regardless. Would you mind going into more detail in how you determined that the touch area is reduced in the iOS 11 calculator?