> There’s no visual indication that there’s more content present in this window—the only way to discover it is to scroll downwards. However, without an affordance to indicate the presence of additional offscreen content, the chances are low that someone will bother to check. > This is why Apple introduced a preference to always show scroll bars.

But the proper solution is to add the info/affordance in that specific instance instead of always wasting space even when you don't use the scroll bar. This would also allow you to have a more convenient wide scroll bar for when you actually need to use it (in very large documents/lists, though currently you can't setup your scroll bar to depend on that)

And here is the main problem with the article - this general approach blocks would block all UI innovation until some browser/OS vendor implemented something poorly (of course, this doesn't mean your implementation will be better, but someone else's will be)