Kids are smart, man. They can usually tell when a vibe is off. Even as a young kid I knew that my mom and dad did NOT fuck with each other.
I never experienced any verbal arguments or overt moments of disrespect in either direction.
But whenever he'd come to pick me up, you could cut the tension and awkwardness with a knife. That feeling that I felt is just something you can't capture on film. I recall moments of just leaving the room to busy myself to do other things while they fumbled through whatever awkward conversations they were having. And then when he was ready to bounce, I'd leave with him and we'd be fine together. Just like time spent alone with mom was just fine.
But Lottie can tell that no matter how much her mom and dad love her, there is an unspoken tension in the room when they're together. She knows it and it makes her feel uncomfortable so she'd rather be doing other things. It's also why she prefers being around her grandparents because it's likely that she can FEEL the love and authenticity in the room versus the awkwardness of being around her parents performative "make nice for Lottie" act.
This was the first episode that I watched back2back between the first and second viewing. Plays even better the second time around when you know where you're being led.