Thats the thing. they claim to be unbiased and then they pull that atrocity... so what are we left to assume of their other videos? not the first and not the last time they will incorrectly nerf/ buff the hell out of a character or just plain get it wrong.
Both Screw Attack and Rooster Teeth are owned by the same company. While the bias card probably played a big role in it, it was definitely more of a giant billboard for RWBY since everything lined up so perfectly. Yang won Death Battle and then RWBY Volume 3 premieres that weekend. Along with a bunch of misrepresented "facts", they were trying incredibly hard to justify Yang's win. And they are very biased, as demonstrated in other videos (Cloud vs Link, Ragna vs Sol, even the TMNT Battle Royale)