At home we see it in him getting side tracked when I ask him to complete simple things like wash your face, brush your teeth and get your PJS on. I will find him at some stage on the process sitting and reading a book. When I ask why he has not done XYZ, he says I forgot. He has no sense of time. Getting out the door in the morning is a chore.
This reminded me of the "flow chart" that contrasts audio-sequential from visual-spatial learners here:
(from this article:
Maintaining Harmony at Home )
I agree that some of your son's activity sounds like a 7 yo boy with a lot of energy & knowledge to share. I have an 8 yo like that & have to remind him at times when it is appropriate to tell people about the latest sea creature he read about & when it isn't. But obviously you want your son to learn to complete tasks & interact in class.
My dd11 liked to stand up while working in 3rd & 4th grade but seems to have outgrown that. She is actually pretty quiet in class. We are having her evaluated soon (neuropsychological eval) for deficits in written expression, spelling, language even though her grades & test scores are high. She has a lot of anxiety when she has to "put things in her own words" in writing. One poster on here suggested stealth dyslexia. Hopefully we will find out soon.
Good luck!