I think these 2 siblings are gonna be near death at some point due to Noh teaching them while not knowing what the actual fuck he is doing. From the flashbacks with Mo Wei we can clearly see there's a precise time to stop, how u must learn to get hit before learning to hit others, but the siblings are doing nothing of it, just randomly beating each other and getting on a bath.
I just hope the author doesn't skip over it and we're supposed to believe that the way Noh passed on the art is correct and will bring no repercussions.