Can someone explain this interview question on the lungs?

[u/Ill-Satisfaction6042]

Im referring to this cambridge interview question https://www.youtube.com/watch?v=I44rE02W0m0&t=585s

My question is

1. What do they mean when you are upright your ribs are sloped at an angle?

How does that cause the front to back diameter to increase?

Im a little confused on the dogs part, ribs are horizontal to your spine, so movement of ribs isn't going to help your chest diameter, so whats the point of the ribs? part. Why woudl movement of ribs not help chest diamter? Im really lost from 7:30 - 9:30 part.

Anyone got a simpler explaination, or can point me to some i.e youtube models that show it in action?

https://ibb.co/Rkm4Yvjw - is this drawing semi accurate, aside from the angles bit?