Agreed, I have tested several time with my 4670 and 4890, for low end card 4670 will gain a lot of GFX score when pushing the clock higher, I think it is because CPU is not the bottomneck for such low-end card, so CPU score is lower, while 4890 score just like normal.
To make it more clear, it is not a cheat, I don't mind making video shot to prove the whole running process for other users to clarify.
Thanks!