The only "evidence" for krillin being stronger than tien is yamcha telling his kid how amazingly strong krillin is. But there's absolutely nothing to indicate it was anything more thtan yamcha trying to make marron feel good about her father or a slight exaggeration by yamcha.
especially since AT no point did krillin ever seem to surpass Tien. He was weaker than tien at the tenkaichi budokai. He was weaker than tien during the King Piccolo saga (and also, he was dead
). He was weaker 3 years later at the world martial arts tournament again. He was weaker 5 years after THAT at the beginning of the saiyan saga. He was weaker 1 year after that when vegeta and nappa arrived.
The only time Krillin might have surpassed Tien was in the days/weeks after receiving a powerup from guru. But Tien always had more natural talent than Krillin, and he also trained more. Krillin trained kind of at a leisurely pace with Master Roshi while Tien was up in the mountains devoting himself fully to his training, and then Krillin stopped fighting altogether so he could raise a family.
I can't see any reason why Krillin would be stronger than Tien.