Levels are "relative" ( yes I know that at first glance that would appear to be obvious, but think about it, they vary with culture and geography )..and also reading levels, and particularly comprehension levels, have been falling in the "West" for years.
Grammatical structure appears to be "optional", with bad grammar and spelling accepted as the "norm",( their, there and they're and also you are, your and you're, appear to be taken as interchangeable on these fora as elsewhere ) ..much to the irritation and chagrin of some of us.
But..in the light of such degradation..
It would not be surprising if Google testers "disliked" what some of them could not understand, due to lack of their own vocabulary ..and if those "dislikes" became folded into Panda in part.
I don't approve in anyway of such "dumbing down"..it bodes badly for our societies ..but if "reality" TV can flourish, and semi literates can run for highest office in western developed countries, and actually attract mass following ! Well, maybe the search engines are reflecting that Rome is being over run ..from the inside, by the self created barbarians :((..
As netmeg says it would be strange if it ( reading level ) wasn't there for a reason ..but IMO it is a very blunt tool..and one which should not be used for general assessment of sites when basic serps are created for presentation ..it should be an end user only modifier.