The issue he’s referring to in this interview from EW’s The Ultimate Guide to The Walking Dead was indeed a departure from anything that The Walking Dead had delivered to that point, with Rick and Carl as the only main characters seen in the issue.
Similarly, the TV episode that Robert Kirkman penned, titled “After,” whittled out all of the characters except for Rick, Carl and Michonne, which was a pretty big choice for a midseason premiere.
It’s easy to see why it stands out in Kirkman’s mind.