Lexile Measures flawed?

Hey everyone!
So there has been a lot of things on my mind lately. First of all, you all remember that I was put onto the Open guard yes? Well we had our very first competition yesterday! I think it went really well for our first show and home show. Problem was that because it was our home show we couldn't actually compete with the other Open guards but we still got judged. I have no idea what the judges thought of us but we certainly made a lot of people cry which was our whole plan anyways so it was a good thing! I also currently have a project that I am doing in my Honors English class. It's where we research an author and then read one of their books and then see how the author's lives tie to the book. The twist is that we have to have a lexile range of 960 or higher. Which brings me to my main subject: Lexile measures. I strongly believe that lexile measures are incredibly flawed in almost every single way. Because of these measures we had to go from book to book trying to find one high enough. The problem is the way that these people determine the lexile measure of a book. Here's a little bit from the lexile website Lexile.com:

"A book, article or piece of text gets a Lexile text measure when it's analyzed by MetaMetrics. For example, the first "Harry Potter" book measures 880L, so it's called an 880 Lexile book. A Lexile text measure is based on two strong predictors of how difficult a text is to comprehend: word frequency and sentence length. Many other factors affect the relationship between a reader and a book, including its content, the age and interests of the reader, and the design of the actual book. The Lexile text measure is a good starting point in the book-selection process, with these other factors then being considered."

This quote makes me very concerned about lexile measures. Its the fact that the age and interests of a reader determines the measure that scares me the most. If it were really determined by that then why on earth is a a 32 page children's picture book have a lexile of 830 but Jurassic Park by Michael Crichton has a lexile of 710? It's very flawed. Lexile measure irks me.
Sincerely,
Tinkerbell