I think you’re right, but there’s an adjustment (an update, isn’t it called?) warranted in two directions.
The absence of sabotage decreases the likelihood of the fifth column existing at all.
But if there is a fifth column, it could be reasonably predicted that there would be evidence of sabotage unless there was an attempt to keep a low profile. If they were to favor this hypothesis for other reasons, as in the classified data mentioned by Frank, then the lack of apparent sabotage would also increase the probability that if the unlikely fifth column DID exist, it would be one which is keeping a low profile. I grant, of course, at the same time, the decreased probability of there being any kind of fifth column in the first place.
“Technically, it proves his belief about science is false.”
True, though in the same way, Eliezer’s success in producing an AI, even according to the dodgy specifications of his dinner companion, would only prove his belief about God wrong, not his belief IN God wrong.
The AI data point would contradict Mr Dinner’s model of God’s nature only at a single point, His allegedly unique intelligence-producing quality.