Hi all,
adding a couple of comments here before starting another “passed the SIE” thread 
I took the exam yesterday and passed; there were a handful of surprising questions (likely the 10 experimental ones) but otherwise the Achievable materials seemed very well calibrated for the actual test. Thank you for the patient explanations, and for putting together these materials in the first place!
My guess? Other vendors probably mix questions on the same topic but for different exams (SIE, Series 7, etc.), or difficulty in the “free sample questions” is biased for commercial purposes.