In general, I think that's a perfectly valid view for you to take. It's not the only one, but it's a valid one.
In specific, this study was a test of reading comprehension, for English majors at a university level. They should be expected to do better with a complicated sentence then "it's really foggy, I guess". Just as I expect someone in film school to be able to give a more detailed review of a movie than "It was pretty good, you should go see it", even though that may be a perfectly acceptable review if a friend gives that to me.
I don't know why you're yes-anding the premise. For this sentence the authors of the study would have been rather more interested whether the subjects would look up the term "aits".
Aside from that, there's actually isn't a lot more to it, which makes it an unfortunate sentence to focus on, because it results in a caricature of the study. "There's just fog everywhere" and "the author is trying to portray a dark, grim, barely visible image of the city" are just barely short of the desired results. It just happens that this mostly straightforward (not complicated) sentence lies between/among many other far less straightforward ones. The problem is glossing where it is inappropriate to do so—and being overly comfortable doing so—which the authors of the study criticize as "oversimplification":
> 96 percent of the problematic readers used oversimplified phrases at
least once to summarize a sentence in the test passage while 61 percent
used this method for five or more sentences. Often, subjects used this tactic
as a shortcut when they became overwhelmed by a sentence with multiple
clauses. One subject disclosed that oversimplifying was her normal tactic[…] Those subjects,
however, who relied on oversimplification became more and more lost as
they continued to read
In specific, this study was a test of reading comprehension, for English majors at a university level. They should be expected to do better with a complicated sentence then "it's really foggy, I guess". Just as I expect someone in film school to be able to give a more detailed review of a movie than "It was pretty good, you should go see it", even though that may be a perfectly acceptable review if a friend gives that to me.