I read some of your thread earlier, and have read a bit more now.
My dd2 sounds a lot like your ds. Absolutely fine a lot of the time, but when she isn't, boy do we know about it.
Dd1 has severe ASD, and so we have naturally been looking out for issues with dd2. She still baffles us, she just doesn't fit any boxes neatly.
But there are enough things about her to concern us, and we have flagged it up to her pre-school, who probably think we are over protective neurotic parents right now (dd2 only started in Sept, and so far all is going well. There have been some issues, but of the type where school would say it was the extreme edge of normal, if we hadn't filled them in on what we were thinking)
My take on this (more aboutnour situation than yours, I suppose) is that, while dd2 clearly does not have the issues that dd1 has, she does struggle with some things. And when she struggles, she struggles a LOT. So I want her to get the help she needs., be that an extra eye out for her when she is feeling sensitive, an extra smile in place of a stern word when misbehaving (dd2 cannot cope with people being cross with her, she falls apart)
And if it takes a label to get her that, then that is what we will do.
I cannot bear to think of her struggling, and feeling on then outside, and not do anything about nit.
But then, I am coming from a position of fighting long and hard to get dd1 what she needs - to not do the same for dd2, because I deem her problems to be less serious (and who am I to judge that? Obviously she does not have the learning disability, completely the opposite, but she understands so much more that it is very difficult to deal with her for very different reasons) would, to me, feel as though I am letting her down.
I want the help in place for her now, before things get too much for her to Cooper with, in terms of classroom rules etc, so that she never has to feel odd, or naughty, or as though she doesn't fit in. I don't want her to get to 8 or 9 and be failing badly (probably socially), and already labelled as a child whondoesnt ft in, before I get her the help she needs.
Sorry, just realised I have written a mammoth Oostende - subject close to my heart today as have been trying to get family members to understand some of this!