This is correct. What's important for industry is understanding the energy balance, i.e. entries and exits to and from the grid. "Generation" is a catch-all term for grid entries.
Generation in this instance means power generation to meet consumption demand. Typically withdrawals from storage are counted as a source of supply to meet that demand regardless of the original source of the power in storage.
A bit of digging in the T&Cs, Companies House, and LinkedIn pointed me to an individual working for the NHS who has put this together as a side project.
I work in this space (https://www.woodmac.com/), mostly with natural gas data but have worked on power in the past so I'm always interested to see if it's anyone I know (in this case it isn't).
Building something like this isn't really that difficult - all of the data is publicly accessible and if you can transform it and pull it into a database and build a front-end app then you're pretty much there. The developer has stated that the main source for this is https://bmrs.elexon.co.uk/, but other good sources of energy data (across Europe) are https://transparency.entsoe.eu/ for power and https://transparency.entsog.eu/ for gas. Also useful are https://alsi.gie.eu/ for LNG imports and https://agsi.gie.eu/ for gas storage.