In her defense, the kids ride a school bus, so she was trying to tie it all in together.
But seriously--she's being interviewed about both of them--she's never speaking straight to the camera. So likely she was asked. But we don't ever really hear the questions on the show though. Just her responses.
Admittedly, I couldn't watch the show--memories was just too much and with the tease of what they would show, I didn't want to sob for an hour over what once was. And I'm sure the comment we are talking about referred to his "stick" comment he said to her and she was offended. In the original episode he did apologize during the interview (and maybe even on a q&a episode, I'm not sure)--but if she was commenting on all the clips and that was one of them, she could have taken the high road and not said anything, but it was a poor choice of words for Jon and Kate has every right to comment on it.