>The report acknowledged that some fossil fuel generators were required to stay running in order to provide flexibility and inertia services to grid operator National Grid ESO during the periods when demand was fully met by clean sources of power.

This is a huge caveat. They're basically saying they outsourced all the things that renewables currently don't do very well to other sections of their grid so they could claim 100% renewable.

It's kind of like saying this one town by a wind farm was powered by 100% renewable energy. Not technically incorrect, but very, very misleading.