That BB getting hit by Law's attacks aren't the same as him getting hit by Ace's attacks. Because while Ace's attacks cause pain to BB due to the heat and some small external wounds, they never Damaged him that much. But Law's attacks Damages him significantly. Against Law, BB spits out blood and goes white eyed. Ace never did that to him. BB's endurance is amazing though.
Because of the attack types.
BB wasnt screaming against Ace for nothing, why are you down playing Ace now huh? All to make Law look much better than what he is?
The fight is currently a mid diff. If it was a low diff, BB would have beat Law already. We will see soon enough anyway. Since oda seems to be intent on showing it and not off screening.
Again why is it a mid diff?
The fight literally just started, Teach hasnt used a single Yami technique on Law yet and you expect him to beat him already? He just used two quake moves, one mid air and the other to block a KROOM.
Just look at Rooftop fight with Dragon Kaido getting battered by Supernovas... I doubt you'd say any of it is mid diff bcs "Kaido didnt beat them already".