Normally FEDs create the front end assets and Sitecore developers chop them up into components. With Feydra, SC devs can create the components as generically styled placeholders that express the data without any styling (essentially as divs). FEDs can update those on their own schedule, breaking dependencies between FEDs and BEDs and allowing for them to work in parallel.
Feydra allows Back End Devs to stub in placeholders for the front end, so the back end can architect and build the actual components based on those the IA has already designed using wireframes (or really simple ones used on every implementation). FEDs can be more efficient because they are working closer to the components, leading to less iteration. FEDs can work on the stubbed components and see how it looks in real time, without waiting for a BED to go and integrate their changes.