Sound has size with respect to its wavelength.
In order for an object to reflect the wavelength, it must be equal to or larger than the wavelength. Of the wavelength is larger than the object dimension it simply diffracts around it.
The pattern on the surface is slight, with maybe a maximum height of ~1.5 inches for the random squares on background surface, with the largest blocks featuring a dimension of ~8 inches.
Making this VERY simple, the frequencies corresponding to the wavelengths of 8 " and 1.5" are ~1688 Hz and ~9000 Hz respectively.
Thus frequencies less than ~1688 will see a flat wall. while frequencies above that would be reflected at a slightly different phase than the energy hitting other sections of the wall.
As far as the edges of the shapes, assuming a near parallel orientation of energy to the boundary surface - easily within the glancing region, only wavelengths greater than ~9000 would be 'seen' and reflected.
The result of such reflections would be a slight comb filtering of the reflected energy, while most of the energy would see a flat wall.
This is a case where a little is worse than none at all, but also where overall very little effect would be experienced.
The surface is predominately limited to aesthetic appeal, while it adds nothing of positive value to the response - and what little effect it does have is detrimental.