Grammar is especially important for the curve breakers. Here is an example of a curve breaker made all too difficult by grammar. From PT 55 https://7sage.com/lsat_explanations/lsat-55-section-1-question-22/
The test is not graded on a curve, but scores tend to conform to a bell curve. I think this suggests that question difficulty would roughly follow this distribution.
... get to the extremely difficult “curve-breaker” type questions. Why? Because ... memory, and outside of the curve breaker questions, you should be ...