sure but that s irrelevant its absolutely fundamental that general covariance has absolutely nothing to do with the physical content of general relativity einstein made a mistake its about time this fact was universally given the weight that it is due general relativity is about no prior geometry it needs to be fully appreciated that co ordinate free descriptions i e the laws of physic are independent of co ordinate systems is a mathematical tautology end of story however they are not independent of actual real physical frames you cannot transform away an arbitrary gravitational field relativity is simply not true according to general relativity