When they say 3x volumetric energy density, that is the actual energy density, which is energy per liter (normal density is mass per liter). Normally people use energy density to refer to energy per kg. Because this is a solid state battery, it is much denser than normal batteries (which are roughly as dense as water). Solid state batteries are smaller but much heavier and this is no exception. It is 33% the size of a lithium battery, but for the same energy it's about 2.5x heavier. Weight is still a much bigger problem for batteries than size- batteries are much smaller than the exhaust, engine and transmission of a car, but also much heavier.
The main limit on specific energy(kwh/kg) for this battery and for solid state batteries in general is voltage. Li-ion is 3.7v nominal, this battery is 2.5v nominal.
1,200 cycles may seem low, but it is actually very good; around 3x the life of current batteries. This cycle life is the time to degrade to 80% maximum storage, at a certain discharge depth and speed. Current batteries only last 300-400 cycles at their specs, but last tens of thousands at 30% depth of discharge.
Problem with the above: in this particular battery, the chemistry breaks down very strongly after it reaches the end of life. Normal lithium does this too, but not as strongly. This stuff may potentially last longer, but it fails much less gracefully. Not in a dangerous way, but in the same way as a normal car often does; once its broken it'll just work worse and worse until it is barely limping.
The temperature capabilities may seem irrelevant, but they are actually a decent problem for li-ion and are the reason lead acid is still used in cars.
Another interesting possibility for glass solid state lithium batteries is that recycling would be very easy. In organic batteries the electrolyte burns or reacts pretty much no matter what you do, but with glass you can plate and unplate cells. Unfortunately due to specific energy, polymer solid state electrolytes are much more likely than glass (also much cheaper).
Edit: IMPORTANT NOTE: this is NOT a fundamentally new type of li-ion battery! Solid state batteries have been around a while (glass, ceramic and polymer), and have specific advantages but low specific energy and power. This particular implementation is a bit higher power and possibly lower cost, but it's just a little blip of progress. Solid state batteries are a good candidate for the future, but they aren't there yet.