I don't know if Blob is correct, but I'd wager the original GR result is bunk, and it sounds like Blob has analyzed the reason why. Quite rapidly, it would seem! There are many examples of people getting aphysical results by blindly applying equations, without understanding the ramifications of their own assumptions. Newtonian gravity works fine for all systems with velocities that are way below that of the speed of light, and the last time I checked, that includes the rotation curves of galaxies!