I did an test scan to confirm my measurements, and it's even worse then I thought
doing a simple scan and letting the software do the aligning and finishing the scan mesh, I imported the STL into Rhino3D and measured the height.

Scan height maximum.jpg
That is 38.55 mm too short !

even the image of the projector is below the 20cm, and around 17.5cm

IMG_2026.jpg

I could rotate the object and continue the scan, but that's is still not what is advertised and I paid for

I am waiting for their answer.