Can I just add, we don't choose our kids and poor behaviour is not always linked to some parental failure. If a child is acting out then that child needs support, not criticism from students and other parents. DS has an unusual personality (autism was suggested and eliminated at one point) and learns in a different way than other kids. He does not need to be pigeonholed or labelled a trouble-maker at this point.
I think we have the full answer here, tbh. Through another child's eyes (reported o their parent) your child is naughty.
You say he has an unusual personality.
She says he doesn't concentrate (again, probably the child repeating what will be said many, many times a day - you yourself has said he needs verbal reminders to behave).
You reply that the teacher says all is OK - well, actually, you know that the teacher has said he does not always behave well but that this is mild (or at least milder than it was) and manly silliness.
She then says something to cover the fact she has two very different opinions of your child's behaviour - and given what you have said in your most recent post, would say that the child's eye in-class observation may well be quite accurate, and actually you know this quite well, but believe that this is based on some underlying SEN rather than being 'naughtiness'.
Definitely not worth e-mailing the other parent about. Definitely worth talking to the teacher 'I know that DS's behaviour has improved with time. Is there still a gap between his behaviour and that you would expect from others his age, and if so, how can we address it together?'