A hatchback's operating function is how well its rear opening, folding seats, luggage floor, passenger space, and driving controls work together in daily use. A large capacity figure is less helpful if you cannot reach the hatch handle, lift a regular load over the sill, or keep the seats you need available.
The best assessment follows a complete trip: approach the parked car, open it, arrange the seats, load your belongings, drive, and unload. Small inconveniences become important when repeated. Judge the actual car with your own passengers and typical cargo rather than relying on the promise of flexible space.