This is conventional DFT which is O(N^3)

Original paper, not a single equation:

https://web.archive.org/web/20240129185108/https://www.owlne...

The N^3 is further reduced by high symmetry. Because structure relaxations are usually convergent, the 2007 DFT and MD calculations can be run on a regular laptop today, maybe even without a GPU!

The discrepancy has been exaggerated by the experimentalist, TFA quotes the original theorist. This is not the first time, and probably not the last time, that c&en has oversold an experimental result.