My experience with this is that processing speed deficits get compounded by 'anxiety' in the given area of slowness, ex: computation. So sometimes a child who is slow can be VERY slow and sometimes just ok - if they don't feel put on the spot.
I myself was considered pretty slow on math facts and consequently grew to kind of hate being asked to do math in my head...although I ended up doing great in math classes where speed of computation was not an issue.
I think my son has gone through/is going through nearly the same: very slow to learn math facts but now in h.s., doing super in geometry. Is he faster? probably a bit. He was tested when he was 8 and again when he was 14, and both times scored < 10th percentile.
Am I faster? well I never got tested as a child for processing speed, but I just did get tested and am at least now above average. So maybe folks grow out of it, but I think it takes ...a while.
reversing a lot of code might be a red flag - what is the 2nd e? does it explain that issue?