Your post doesn't fully convey what they're doing here either. According to the article, it is still possible to package extensions with a software installer,

Your post doesn't fully convey what they're doing here either. According to the article, it is still possible to package extensions with a software installer, but now when the user runs their browser they will be asked to confirm that they want the extensions to be added. So it isn't really blocking those extensions, which I think is a good thing.