I also had the same thought while watching the karna part today!! He was really respectful towards him!! I dnt expect him to blast on suryadev like he blasted on kunti coz its understandable as he is god and he couldnt have claimed karna but atleast a question on karna's part that why even u didnt tell me the truth would have been nice!!
He had no problem in calling suryadev pitaji but had all the problm in the world calling kunti mom, saying it is injustice to his radha maa but all is good for adhirath!!