Ya, I specifically remember solving word problems in school / college and getting distracted by irrelevant details. Usually I would get distracted by stuff that _seemed_ like it should be used, so maybe cat facts would be fine for me to tease out, but in general I don't think I'm good at ignoring extraneous information.
Edit: To be fair, in the example provided, the cat fact is _exceptionally_ extraneous, and even flagged with 'Fun Fact:' as if to indicate it's unrelated. I wonder if they were all like that.
I had always assumed that the extraneous information was part of the test. You have to know/understand the concept well enough to know that the information was extraneous.
From what I remember of school, extraneous information was rarely included and the teachers who did add extraneous information seemed to do it maliciously.
There was one math class at a private school I attended that was the exception. The textbook had identifying relevant information as part of several chapters.
Edit: To be fair, in the example provided, the cat fact is _exceptionally_ extraneous, and even flagged with 'Fun Fact:' as if to indicate it's unrelated. I wonder if they were all like that.