The training comment didn't bother me. H and I have both "trained" each other to do little things that are important to the other or not do little things that irk the other. I talk too loud and it bothers him, so I try to tone it down. He has learned that apologizing is important to me, so he does it.
"Training" isn't the word I would use because it carries a connotation of disrespect when applied to a relationship of equals, but I agree and I get what OP meant. It's not training so much as each party communicating preferences, expectations, and needs and in turn making the effort to change unkind/unwanted/easily misunderstood behaviors to help preserve the harmony in a relationship. In my marriage we have both changed or dropped certain behaviors out of a sense of love and respect for each other.
Yes, H is great at apologizing. He's way better than me. I've learned to say I'm sorry over my years with him. I use to be a pretender and act like nothing never happened. H called me out on it in the beginning of our relationship and continued to until I automatically apologize almost ever time. In my case it was about whether I'd rather be right or happy. At first I was so stubborn that I wanted to be right. Now I'd rather be happy and if that means apologizing even when I was 'right' in my side of our argument/disagreement/discussion, so be it. We always both apologize (even if it takes me a few extra minutes) and then start our discussion again in more calm, rational tones.
My H apologizes when he's in the wrong. In the situation you described, he might apologize on his own but if I was really upset about it and said so (which I probably wouldn't be in that situation), he would definitely apologize. We are both pretty good about saying sorry if we're out of line.
He will apologize usually, but I also don't hold onto it. Ex: last night he left work a little late (unplanned) and I asked why because we needed to go to the grocery store, etc. He got a little snippy, but still answered the question. When he picked me up to head to the store, he said he was in a weird mood and apologized for his response. I didn't think it warranted an apology, and told him that. This is typical H.
He hates pretending something didn't happen, though.