Being slower in work suggests a problem in something, which may or may not be attention.
My DS looked an awful lot like this at age 9. He's now 13, and things that were minor issues then became massive issues when he entered a middle school gifted program with a ton of complex writing demands. It was the difference between being slow and a bit of a space cadet when younger, to now being unable to get any writing task done in a remotely reasonable amount of time. Attention deficits play a huge part in this, but we're pretty sure there's all sorts of other things at work too (like probably expressive language).
So I would say you want to keep a really close eye on things over time, but as to whether more testing/ diagnosis is necessary right now, that really depends on a lot of factors. Is his slowness completing work, or his trouble controlling his attention, contributing to his anxiety or frustration? Do you see changes in behaviour that might reflect increases in underlying anxiety (e.g. in sleep, eating, socializing, or more sensitive/ reactive)? Does he miss things he wants because he is too slow or wasn't paying attention (for instance, friends leave without him because he takes too long to get ready; or he misses a desired school activity because he didn't notice the announcement; or he starts to feel like there is something wrong with him because other kids can easily do things he is struggling with?) Has he been checked for fine motor issues before? (the areas you mention could be fine motor as much as attention).
With 2E kids, issues tend to drive up the anxiety long before they show up as achievement problems, so it's important to keep an eye on the overall state of the child. And recognize the cause-effect relationship can be less than obvious. And also, that high levels of anxiety can look a whole lot like inattentive ADHD - but that the ADHD can drive up anxiety. It's not easy to sort out whether you are dealing with one, the other, or both.
If anything is giving you cause to worry, then understanding exactly what is slowing him down could be be helpful, sooner rather than later. And given his age, if he is dealing with something specific, then the sooner any accommodations he requires are documented and become standard practice for both him and his teachers, the better. Middle school tends to come with a huge ramp up in the number of teachers, the complexity of assignments, and the assumptions for independent management of work and time. And much more self-consciousness about using new accommodations.
On the other hand, if he is happy and getting the supports he needs with or without an additional diagnosis, than maybe more testing can wait until there is a clear problem - and that may not ever emerge. Also, since ADHD is so commonly co-morbid with ASD, you may find it's already being well-addressed, and may not require a distinct diagnosis. It's always tough finding the line between needed early intervention, and needless creating problems where they don't actually exist. But it's usually good to trust your parental instincts. If all feels well, good. But if something is worrying you, act on it.
