I don't remember exactly what Zach said but it was pretty much that he hasn't been there for them since they were 5 years old so it was no surprise that he wasn't there for them at the graduation...something like that, so I took it that he was referring to Matt always being absent, not necessarily that he wasn't there for them emotionally. But he was very direct about what he said and I definitely heard some resentment in his voice, or just acceptance that that's how his father has always been and probably always will be.
What I couldn't understand was why Matt was late for the graduation, it didn't sound like he was doing something else, business or otherwise, it sounded like he was at the house and just didn't want to get there early and have to wait, he even said during one of the interviews that he doesn't like to ever wait and he admitted that he was late getting inside because he cut it a little too close and there were a lot of cars and nowhere to park. Now I'll admit, I'm known for always being late, but to my childrens graduation??? Don't think so.