Hello Vincent,
Thank you for providing the sample data.
Seems like it was my fault and 16-bit tiffs on input really produce 8-bit texture output. So the only way to overcome this problem is to convert the original images to 32-bit, it will result in 32-bit output.
We will consider to possibility of fast implementation from 16-bit input to 16-bit output for texture generation, but it will take some time.