The first step is decoding the raw, which is usually just a derivative of the TIFF/EP standard with additional metadata fields and proprietary compression. Almost all RAW files are dead simple. They are literally just a TIFF image of the raw mosaic, with additional text describing what the lens was used, what white balance settings were used, etc. The second step is processing the data from the raw file. This is exclusively on the processor and here quality varies quite a bit. Decoding most often is really simple. It's what you do with the data that you have successfully decoded, this is on the raw processor. Decoder and processor are two entirely different things.
Now the article muddies decoder and processor. If I understood correctly, it was talking about generating previews in the file manager on macOS, and the other one is just a processor. Now, if you were to just decode RAW files, you would essentially just get a green picture, because if you zoom out all the way on a mosaic, what you're left with is completely green. So, of course, it needs to do some processing that you can actually view it, how it's meant to look, and not just in false colour.