In my experience a lot of people are very bad at paying attention to what it says about session difficulty in the program. I was on the program committee of a tech conference for a number of years and saw a lot of feedback forms from people who clearly don't understand what words like "introduction" and "deep-dive" (and their numerical equivalents) mean.

We tried a lot of different approaches and you still end up with some audience members whose expectations are seriously out of tune with the content of sessions.

Of course, sometimes there's fault with the presenter too.