It'd be nice if this blogspam linked to the source so we could verify details.
[1] https://coryton.com/lab/news/mazda-using-sustain-100-per-cen...
I looked at several other sources covering this and they're all similarly quiet about what the fuel actually is. Looking at they supplier's (Coryton's) website, they boast about 'bespoke' synthetic fuels. So I'm guessing it's Mazda that's being shy about the details.
There is another engine design, a linear piston engine, which is just a piston connected to a magnet and coil. The engine generates electricity (at a constant speed, constant load) and this is fed to an electric motor. So the car is a hybrid. It's more efficient than a regular engine (which turns a large crankshaft etc.) and the fuel probably can be more finicky since the combustion cycle can be tuned for one operating point.
Let’s not even talk about all the things in the fuel system that seem to have a shorter life with ethanol involved, particularly injectors.