Generally speaking, the burden of proof lies with someone making a claim. A claim was made that g12+5 Savage can beat a g13 GG.
A video was submitted of a g12 Savage beating a g12 Grievous, which does not support the assertion. Also, to claim Savage can "breast his rear" implies that the Grievous would be well modded - so requiring a poorly modded Grievous to win means the initial claim is pretty meaningless.