So the right side is higher in altitude, as it is the second stage. However, it has two cameras, alternating and showing two different vantage points — one shows engine in line with earth, the second shows an engine with space behind it and a much smaller section of earth in the frame. Smaller section has correspondingly less arc, so what length of arc you can see looks less curved. Over time though, earth pans across both first and second stage cameras, just at different times, and you can see the curvature in both cameras of the second stage. I agree this can be confusing.