Exactly this. The moment I read the initial claim of sentience, I wrote that they could have asked it "Why did you blow up the whole world?" and it would generate a plausible answer, and could probably describe exactly how that was accomplished.

I don't believe the engineer really believed what he was saying, but probably attempted to gain a little fame for himself. Instead, he gained notoriety as a gullible man full of bonkers stories. He shot his own credibility down.

In part of his writeup, he realized LaMDA would "lie" (a purposefully chosen word that formed the basis of even more leading questions...) about its history, eg being used in a classroom when it never had been, and its generated response was that it made people feel more comfortable.

How could he notice that it generates untrue but plausible statements when asked about events that didn't happen, but not be able to notice that the exact same thing would happen when asked about emotions, etc., that also didn't happen?

I'm reading a book called Blindsight about aliens that are very similar to this. Maybe this engineer has read it, and his imagination has gotten the better of him.