I have an ok IQ and have aphantasia. It makes some questions harder I am pretty sure - I am always second guessing and re-checking because I cannot retain even a small amount of visual information.

I only found out about aphantasia early 2018. I had always suspected there was something different/difficent and went to a university study, and just reaffirmed my IQ and discovered that I reallly get slow on some tasks - I find the answer fast enough but I have a lifetime of distrust on my processes, so just out of habit do double or triple checks (which dont really make better answers, just verify what I am writing is what was meant, I guess). Of course, no one knew about aphantasia at this point.

I failed geometry in jr.high hard. It was almost impossible. But making and passing calculus was relatively easy (long story short: parents moved, lied about passing geometry).

I have mild dyslexia, so I think that mixed with the other just makes it reallly hard.