Am I wrong thinking the intervention shouldn't have happened before direct confrontation?

So one of my friend build up some resentment towards me. He didn't like that I was too blunt, insensitive and a little bit neglecting. I didn't know he build up this much resentment, and without forewarning I was called to an intervention to talk about issus they had about me (him and two other friends in the same friend group. He is closer with them than me). I asked them what is was about, but they didn't want to tell me, because it was something they want to bring up at the intervention. Basically I wasn't allowed to mentally prepare or think about my explaination the week I had to wait. It was a emotional draining period.

Is it wrong thinking an intervention should come after a direct confrontation? I felt disvalued because I feel they talked behind my back and arranged a group effort.