Recently I needed to summarize about a thousand lengthy documents, and then translate those summaries into Mandarin.

I spent about a minute composing the prompt for this task, and then went for a cup of coffee. When I got back the task was done. I spot-checked the summaries and they were excellent.

I thought this was amazing and magical at the time. Am I wrong? Or is it simply the AI making me think this result was amazing and magical?

This is an LLM's bread and butter so I would hope it does a decent job.

You just spot checked it, so how can you be sure how accurate it is. Was it 80% accurate? 90%? 99%? And how does the domain influence the accuracy requirements?