Jen J is correct. If you tank on the MCQ, or if you knock them out of the park, your SIMs have no bearing on that. Although, maybe they should….food for thought! I've never quite understood the logic behind adaptive testlets. Instead of giving “a testlet of medium questions” or “a testlet of hard questions”, they should simply give a mix of easy, moderate, and hard MCQs, just as they do with the SIMs (which usually are a mix of like 1-2 easy, 2-4 medium, 2-3 hard.)
The pattern seems to be that if you fall down on the MCQ, you can still pass if you haul ass on the SIMs. And, likewise, if you perform well on MCQ – like get 90 percent or more correct – you don't have to do as well on the SIMs. At least that's how it was until April 2017 before they changed the score weights. Nowadays I don't think it's quite so much that way since the SIMs are all weighted more heavily. And, that the SIMs are broken into separate testlets now.
BTW – you may have done well on the SIMs and not as well as you thought you did on the MCQ. It happens that way sometimes. When I took BEC, I performed “Stronger” on the MCQ but I was ready to just walk out after finishing the MCQ because I found myself guessing on about half of them.