and make it faster to react?
No.
The diffusers can expand the area of one LDR
No but it expands or spreads out the light from the laser from a spot into a larger area and therefore can match the light collecting area of an LDR.
Can you show me a link to those diffusers please just to have an ideia
It is not "those" diffusers, it is just any translucent material, maybe two separated by half an inch.