It is an interesting stone isn't it? The other take on it is that the cup marks may represent star constellations. Speculation about 'religious' practices is just that - speculation. However,I think it is fairly safe to say ancient peoples marked the turning of the year (solstices/equinoxes) and studied the constellations - which would have been so very much more visible to the naked eye than in general today.
The interesting and informative aspect is that the abstract rock art of Britain doesn't appear to represent constellations or the night sky at all . We might expect it to and should really be able to squeeze some sort of "possible" representation out of the the huge number of possibilities but none are convincing .