This is very true! I could have been more careful/precise in how I worded this. I was really trying to just get across that it's in a sense easier than some tasks that can be much more open ended.

I'll think about how to word this better, thanks for the feedback!

This is extremely true. In fact, from what we see many/most of the problems to be solved with LLMs do not have ground-truth values; even hand-labeled data tends to be mostly subjective.

I think they're just saying that data extraction tasks are easy to evaluate because for a given input text/file you can specify the exact structured output you expect from it.