DLSS also serves an additional purpose in that the DF team and I strongly suspect that being able to run ray tracing at a lower resolution (before being scaled up to your display's native resolution) is the key to making the technology more performant: Nvidia's very own Star Wars Reflection demo - heavily reliant on DLSS for its 1440p and 4K support - proves the point. We'll be taking a closer look at DLSS very shortly, and we'll provide screenshot comparisons and a deeper look at performance, where one or two surprises are thrown up through more granular frame-rate testing.
https://www.eurogamer.net/articles/digitalfoundry-2018-9-19-geforce-rtx-2080-2080-ti-review?page=5