"He doesn’t like being rushed. Generally in life but I just figured that’s common for most kids this age. "
No, I disagree. Well, partly. Many of us don't like being rushed. I mean who likes being rushed? I know I don't. In certain things.
So, maybe it's a processing issue. But even then, even if tested and then given more time in exams, he'll still need to speed up. Fact. In life. So look up techniques for that.
But also talk to him. He maybe very laid-back but in life there are certain things that need to be done quickly and promptly. plus not all children are very laid-back. Some are extremely competitive and want to get it done as quickly as possible and take pride in getting 99% or 100% especially in maths questions which are often fundamentally right or wrong with the correct answer and you can easily get a very high mark.
he doesn't want to, or can't, or maybe has no interest in this aspect, or another reason? and that's maybe his personality and you need to talk to him about techniques and actually wanting to speed up, wanting to show what he can do, show the best he can do, as a sign of success, in order to proceed.
Very bright children who just grasp concepts easily, and then fly through exam papers, happy at challenging themselves as to how quickly they can complete it all, clearly have a different mindset.
Talk to him, I think there's lots to explore here.