I knew that Square redesign had this kind of menu for desktop users as well and I found it odd and I still think that it is a strange solution. Now, I stumbled on this website that has the same kind of menu. I guess it's related with the idea of having a responsive website, but this solution doesn't take desktop users in consideration. So I was wondering, what are the big pros of this solution that cost the experience of desktop users?
I think both sites could afford to make the animations a bit faster as they hinder all users at the moment.
However I wouldn't say they haven't considered the desktop, but it certainly is a mobile first/content is king style they have adopted. Nor is it necessarily designed at the expense of the desktop experience, it just hasn't fully taken advantage of the larger screen real estate available.
As for pros
- The site can be used as a strip down the edge of the desktop like an always accessible app
- Forces a rethink of what is essential and removes any visual element that is detracting from this
- More likely to load faster for all due to reduced complexity
Focus on the core users, make accessible for others
I think why may be your reluctance to embrace these solutions, is that they haven't enhanced the desktop layout enough. The extra expense to optimise a desktop experience may not be warranted for products such as square, which are heavily mobile related. It is possible that 'Earnest' are also predominantly accessed or have a greater need to focus on mobile and have designed accordingly.
Like any project it is important to know your users and how they are accessing (or could be accessing) your content/service and cater to that. A loop of designing and testing is likely to be your best guide. Perhaps the delightful experience of the animations outweighs the cost of not showing the menu expanded? Maybe they don't run their browser full screen and appreciate that they don't need to scroll as much because of the condensed nature of the navigation and content.
Further Reading Suggestions
I would suggest reading up more on 'mobile first' design and see how the pros and cons weigh up. Also consider reading some early and late Donald Norman books to see how he has changed his tune from a 'form follows function' to a 'form follows emotion' approach as research into understanding the brain and particularly the role emotion plays in users experience.