I don't think it's sinister at all personally I just think it needs clearing up. How was their communication, did he not know why she was so organised that morning or why she put the kids/dogs in the car? It's not like he was still in bed...mind you I'm not married, I have no idea how much spouses (or long-term partners) communicate! It just seems like something they'd have had to communicate about since it means the other person doesn't need to do something they normally would. I mean all this stuff was asked of him in the interview, it's just he didn't really answer what exactly happened that morning did he? And he didn't say "I can't remember" he just kind of glossed over it and talked about the usual schedule that happened most days. We don't know their breakfast routine or anything, like did they have any sort of conversation or was she just straight off? It could be something like she was in a bad mood or they'd had an argument and understandably he doesn't want to mention it because that would arose suspicion. Or maybe he was just so laid back (although I don't get that impression tbh) he didn't notice.