The article makes it sound like the scrollbar has been removed and is only accessible if the setting is turned on. Seems silly. All you have to do is start scrolling and you immediately see the scrollbar.
"until you start moving down a webpage" is literally in the second sentence of the article.
E.g. "The first and basic thing is it allows you to grab the scroll bar and move down the page quickly. You don't have to double finger scroll over and over to get to the bottom of a very long page. You can simply drag and pull it to your desired location."
You know what? if you move your mouse all the way to the right to scroll with the bar you can also scroll for a fraction of a second to reveal it so you can grab it.