It appears to be a common trend though, I guess because most content is now on apps and those websites only advertise apps or services.
The layout is really up to you.
In retrospect I could have worded the title better.
> We’ve done our best to prevent breaking changes, but we had to sneak some in. Regrettably, we’ll also have a few more coming in Beta 3, too. However, we’re clearly outlining all of them for you to make the upgrade and testing process as easy as possible.
Source: https://blog.getbootstrap.com/2017/10/19/bootstrap-4-beta-2/
https://github.com/HackerThemes/theme-machine/blob/master/th...
https://github.com/HackerThemes/theme-machine/blob/master/sc...
which is imported in the file that you linked. That's all in terms of SCSS. Then the gulp task runs the SCSS build and the autoprefixer.