No Mac user has ever thought "gee, this third party design is so much more tasteful than something that follows the HIG!" Apple is right to keep designers on a tight leash.
Apple stopped following the HIG a long time ago. Even Gruber admitted it back in 2011. http://daringfireball.net/2011/01/uniformity_vs_individualit...
That article, by the way, is about a good counterexample to your point (Twitter for Mac).
If devs all go off in their own direction, then users have to re-learn the UX for every single app.
Apple envisioned a purpose for the bar. If all apps convey a consistent message about what the bar is there for, it will become easy to use. You will know that when you intend to do a certain thing, the bar will be there to deliver this predictable functionality. What it's there for will be obvious.
If on the other hand everyone uses it for different things, then the user will receive mixed messages about what the purpose of this thing is. There's no pattern. There's no way to develop a reflex without repetition. In this case it's not repetition of a certain action but a theme. Part of using the thing is conveying a consistent intent ANY time the bar used so the user receives clear messages. It's about being a good citizen. You sacrifice freedom in how you use the bar so it becomes natural for ANYTHING you might use it for on your computer.
It's to avoid the situation of taskbar icons on windows. These have no fucking purpose.
As the Web proves every day, the problem is with designer and companies that for some reason treat the digital medium as if they were designing a goddamn paper poster - an ad that has to look pretty, instead of a tool that has to be useful.
PS You know who decided what Reader Mode should look like? Designers and typographers.
http://images.apple.com/v/macbook-pro/j/images/overview/touc...
Maybe wait to actually use one before trying to rally the mob with pitchforks and torches?
https://en.wikipedia.org/wiki/Soft_key
https://en.wikipedia.org/wiki/Virtual_keyboard
I personally don't feel the need to be that pedantic — since I've used both good touchscreen keyboards and wretched hardware, I'd prefer to focus on the quality of any specific implementation rather than philosophical debates about the nature of a “key”.
That's why I was making the distinction; I feel like you chose the interpretation of "key" that could be trivially dismissed, rather than what they probably meant in the context of their complaint.
Luckily, we've got two implementations that we can compare, and that it would be logical to assume we're talking about: The Touch Bar and the row of keys that it replaced. The TB adds some pros: continuous (slider-like) or discrete (key-like) behavior, display of dynamic information, and general flexibility. It has some cons too, though: Lack of tactile feedback makes it impossible to use without looking, it potentially requires extra key-presses (and glances to the keyboard) to use the old functionality, key placement isn't predictable, etc.
My point being: It's reasonable to assume that the comment you originally replied to was complaining about the difference between virtual and physical keys, but your reply basically said "that doesn't matter, because you can simulate the missing keys".