I'm no expert either just seems to me to make sense since speaking requires complex motor planning. As I understand it, motor planning refers to the process in the brain of taking a decision to do something that requires movement (I decide to say "hello") and translating that into the action (I say "hello").
I could see motor planning affecting speech and language in lots of different ways - everything from basic articulation problems to more complex problems with long sentences that require many consecutive motor actions.
I don't mean to say that there's something wrong - just wondering out loud I guess. I know with my own kids that I had no idea they were having so much trouble with language tasks that could be helped through speech therapy until they got speech evals. They could "talk" well enough to get by in life and it just didn't occur to me that there was something more going on than slow processing.
If you're concerned about it, here's some of the questions you might ask yourself - or him for that matter - about his speech and language usage:
Is he able to:
-talk freely when he wants to, especially when stressed or upset
-say what he wants to say without struggle or stuttering
-answer questions promptly with no unreasonable delays
-tell a story from beginning to end with all the information in the right order and without you having to ask lots of questions in order for you to understand the story
-focus on the important parts of the story and leave out non-essential details when appropriate
-follow complex 3 step directions
-recognize when he doesn't understand directions or information and ask for help
-understand metaphors and other non-literal speech/references without trouble at an age appropriate level
-use and understand pragmatic language accurately
-determine the correct interpretation of ambiguous messages based on the social context or non-verbal clues
-understand and use humor appropriately
Sorry - I think I got a little carried away.
I'm sure you've got the idea.
Hopefully the sensory clinic will be helpful. Maybe you could ask them what they think about whether he would benefit from a speech eval.
Patricia