+1. The way I think about it is that signed exchanges are basically a way of getting the benefits of a CDN without turning over the keys to your entire kingdom to a third party. Instead you just allow distribution of a single resource (perhaps a bundle), in a crytographically verifiable way.
Stated another way, with a typical CDN setup the user has to trust their browser, the CDN, and the source. With signed exchanges we're back to the minimal requirement of trusting the browser and the source; the distributor isn't able to make modifications.