This is going to be a disaster, for some time. Yes, we all going to get used to it, but this starter pack, which I hope it’s not going to be released, will be a disaster for most user.
WordPress gives too many options for a sidebar of a website. WordPress gives you the option to write a page content on the sidebar with all the available blocks as the content creation.
Secondly, there is a little confusion with widget block and grouping. You’ll need to group blocks to work as a widget block. A theme designed with a widget separator will get a hell of lot of support requests.