As with most misunderstandings/disagreements/arguments in the programming world, this confusion arises from people in different contexts using a tool for one purpose, but not realizing that other people are in different situations trying to achieve different goals with those same tools.
(Specifically, if you are an agency or freelance designer/developer, and you are building a bunch of different sites, then this tool does not serve any useful purpose... but if you have an underlying "design system" and a large company with lots of different products all sharing the same basic design, and a large team to go with it,then this starts to make a lot more sense.)
I do think that design systems can be helpful for smaller, or even 1 person teams as well. It helps you to apply meaningful constrains for your design and reuse common components across the product to shorten development times.
With the library we have both designers and developers can construct completely new views or modifications fairly fast. https://twitter.com/karrisaarinen/status/849733176150773761
Where the React-Sketchapp comes in is help us to keep the system up to date for designers, and in the future build other tools that can help the design workflow.
1.) Design your thing in Sketch
2.) Code your thing in a text editor
3.) Port your code over to this new tool to see it rendered in Sketch?
Like I said. There's some value there (accounting for the changes between 1 & 2), but the workflow feels weird. Maybe someone from AirBnB design can jump in and enlighten me.