AITAH for not apologizing to my step son?

I ( F,34) have been dating my boyfriend ,David ( M,37), for about two years. We have been living together for the last 8 months . David’s wife died when his son ( M,10) was 6. His son is a very affectionate kid. He is very polite and I don’t even need to ask him to help around the house . He knows his assigned chores and always volunteers to help out.
Here is the thing : he likes correcting people , he gives us random scientific facts , he loves to be part of all the conversations and give his opinion. He likes to be centre on attention . He interrupts people and if you stop him he immediately apologizes but do it again. This is very irritating. I asked David to test him because there is something off with this kid. After spending thousands of dollars on private testing , psychologist said he is highly gifted. I guess that explains being bored at school and volunteering to be teacher’s aid ( his teacher started a teacher’s aid and asks kids with stronger academic abilities to pair with struggling kids and help them out with their homework).

He has been going on my nerves lately . Yesterday, we were watching the movie Ice Age. He decided to give us random scientific facts about ice age , evolution , dinosaurs,.. I snapped ! I told him no one cares about his dumb facts! You need to learn to STFU sometimes or no one wanna be your friends soon. He said “sorry ma’am “. Then went quiet . He has been quiet since then ( thank god!) . When he went to bed , David said I was very harsh to him. His brain works different than us. He needs to learn to regulate his emotions but you were cruel . You owe him an apology . I told him I’m not apologizing to a kid and I meant it . I’m so upset because David basically telling me that he doesn’t have my back . AITAH here to tell a chatty kid to learn to STFU ?

Added later : I should have known as soon as I mentioned he is not my kid, bleeding hearts will attack me! STFU! I’m done