Many thanks @Ootohere for the comment. This monday I did a 11%-95% charging, the 11%-80% took 44 minutes so almost the double than the reference. And this speed is quite permanent on DC between 10-80%. After several charging, it seems this is the real capability of this car...
The car and the charger as well is always informing you about the actual charging capacity, and this value was never higher than 21kWh.
Factory values:
The usable capacity: 100% = 19,7 kWh so 10-80% means 13,79kWh / 26 min results 31,82kWh in average in the best range.
It is unclear what value is displayed by the car and the charger, since ~12% charging loss is coming into the equation on DC. According the Skoda communication I assume they are stating the real charge and not the consumed from the charger.
My values
15,22kWh / 44 min results 20,75 kWh in avg which is corresnponds with my experience.