I had a similar thought when I read the texts.
The first (b&w) text was just harder to comprehend due to esoteric words, lack of thought direction, and several personas. I couldn't understand what author was trying to say.
The second (colored) text was about a female teacher and had a common vocabulary and a straight-forward theme with one character.
According to them I read 11% faster. Although I guessed on 2 out 3 questions, compared to knowing all 3 from b&w text.
Thus, I call BS on their testing experience. These two texts are way too different. And picking an easier one for beeline text does a disservice to this hopefully legit fast reading method.