I am not quiet sure whether this is intended or not, but the bone block is handled as if it was a transparent block and I see no reason for it to be like that. It is basically just a pillar block and in general pillars are not transparent.
Also it is a full block (16x16x16) and it does not have transparent textures.
As a result of that, you cant place torches, redstone dust and things like that on top of it (see
MC-102051) and it gets rendered even when it is inside of other full blocks. That may cause some tiny amount of unneccasary lag.
Obviously it also lets light through because of that bug.
The only advantage I can see here is that you can spot it even in survival pretty easily by using "features" like
MC-57930 if you are in desperate need of bone meal.