It's a question of intent. If I were a Chinese sub skipper who had stalked a U.S. carrier then the last thing I would do would be surface within site of the target and advertise my capabilities. I truly think that there is every likelyhood that Chinese skipper had no clue he was as close as he was.
No doubt.
There was absolutely NO reason for the Chinese skipper to knowingly show himself. By doing so, he compromised whatever tactical and technical prowess they obtained.
It’s not Chinese culture to broadcast their capabilities. They consider patience and time to be on their side.