10-13-A (B backstroke)

[bambam]

Trying to make sure I understand 10-13-A/B flat backstroke shoulder turn.

My understanding of this variation is that it should be as flat as possible without moving the stationary head - is this correct?

Also, I don't see very many swing sequences where the backstroke looks as flat as the picture in the book - is 10-13-A common?

Thanks!