Yes, it is normal. The time it takes to thicken depends on the water added. It is recommended to use a mineral water with low amounts of calcium (<100mg/l).
Thickening also comes with time: after a few hours, the natural origin activates and makes the cream more unctuous.
The cold temperature of the fridge also gives more weight to the cream.
Ma Crème Nature is a 100% natural origin homemade cream, it is normal that the final consistency is different from a commercial cream.