"Since 2011, the United States National Aeronautics and Space Administration (NASA) has excluded the Chinese government and China-affiliated organisations from its activities, including using funds to host Chinese visitors at NASA facilities."
No, the current declining has nothing to do with the one child policy which has been removed for years. But the editors of the Economists obviously have more love for one-child-policy-topic than any real reasons.
About eighty years ago, the US assembled the top minds of nuclear physics, and the US military knew the potential of creating a weapon out of physics, then BOMB. Now the situation is the same, it's reasonable to think the US is the most advanced nation in cyber weaponary.
In China, Toad King Warship (膜蛤文化) is very popular in some people, espcially young ones. There are tones of memes and internet jokes around that and obviously nobody gets into trouble because of it.
I don't know why your interviewer told you he was afraid. A wild guess is that he was one of those young people who loves Toad King Warship, and your ice frog reminded him of it. But it's hard to explain it to a foreigner (or he find it inappropriate to mention in an interview. it's a sub-culture anyway). So he just say he cannot say about it. As you further asked for reason, he gives you the answer you have in mind, by acting as victim of surveillance state (another culture thing).