The headline is misleading, they haven't approved the design yet. However, they've been able to certify that the reactor does not need a certain standard of backup power supply and electrical circuitry due to the passive safety features of the design. This standard essentially requires that nuclear power plants have a connection to the grid and an on site backup generator to safety systems that are on completely separate circuits from the nuclear power plant electrical generation systems.
Not having to do this makes it cheaper for NuScale to deploy powerplants. And it also makes it easier for them to build powerplants in remote places where a connection to the electrical grid is not available[0].
FWIW, you can often find this by going to the Google cached version of this page (in this case: "U.S. Nuclear Regulatory Commission Approves NuScale Power’s Advanced Reactor"), though I agree, it would be useful to include.
Not having to do this makes it cheaper for NuScale to deploy powerplants. And it also makes it easier for them to build powerplants in remote places where a connection to the electrical grid is not available[0].
[0]https://www.nrc.gov/docs/ML1616/ML16169A148.pdf