The only way people brought up SN in the other thread was in the context of 'this is what should be done assuming there is no SN'. The reason for putting it this way is that children do occasionally get unfairly punished for things which they cannot help, because they turn out to have mild behavioural SN. It's about wanting to make the best suggestions for a child by making sure that we have understood all the issues.
Those of us who have children/friends/children's friends with behavioural issues have heartbreaking stories of children who have gone on being punished for years because nobody understood that they had genuine SN problems. My friends' dd had done several years in primary school before anyone realised she had mild Aspergers. Naturally, before that she got punished for the same things as everybody else. And she got punished a lot...
You speak as if you thought there was something offensive about the suggestions of SN.
To rephrase it:
if your son has any SN, he would need special consideration and a line of extra strategies to distract him before problems happen
this probably would require extra resources
there is no way a teacher can manage to do this with every single one of a class of 30 children
an NT child who kicks and spits needs to be dealt with in a more summary fashion.
IME this means missing playtime if you play up or show aggression (as the mother of the child who was at the receiving end of aggression, I was profoundly grateful for this!); it means being taken out of the dinner hall if you are disruptive; it means being able to cope with disappointment without kicking and spitting at the teacher. This is what most 4yo are expected to cope with.
therefore it is appropriate to the issue to establish whether he is a boy with need of extra help or not. There is nothing offensive about this! it's about wanting to do whatever is best for him.
Please don't be offended if the school mentions SN; they have to explore all options. It seems your boy is a little unusual, and that you are also asking for him to be treated in a way that is a little unusual. They can't do this if they are not allowed to discuss this openly.