I’m not familiar with the particular theme you mentioned, but there may be a couple of different answers to your question, depending on what you need to do.
First, remember that just because a file has an extension ‘.scss’, it doesn’t mean that it is actually SCSS. The browser will (usually) load anything as a stylesheet, regardless of what extension it has - and some people use that to load server-side dynamically generated stylesheets, for instance, with PHP. Indeed, there is nothing in the code you pasted above that is non-standard CSS.
Now, there are indeed a few different ways to have your browser directly load pre-processor stylesheets, such as LESS/SCSS files.
I hope this helps!