I'm so sorry you're going through this, your son is lucky to have you advocating for him, but as you stated, you shouldn't have to been telling the teachers what they should be already doing!!
I am in a similar situation, my son just started jk, and I suspect he may be similar to your son. He is extremely gifted but also has some 'quirks' about him. The first teacher meeting, she told me she was concerned as he is often daydreaming and cannot answer simple questions when asked. Yet he comes home and memorizes the times table for fun. We see a specialist in paediatric development tomorrow.
Good luck, I hope your meeting goes well!