You may take normal relief from an Immovable Obstruction without penalty, by dropping the ball within the bunker. Or you may drop the ball outside the bunker with a 1 stroke penalty.
Extract from Rule 24-2b
(ii) In a Bunker: If the ball is in a bunker, the player must lift the ball and drop it either:
(a) Without penalty, in accordance with Clause (i) above, except that the nearest point of relief must be in the bunker and the ball must be dropped in the bunker; or
(b) Under penalty of one stroke, outside the bunker keeping the point where the ball lay directly between the hole and the spot on which the ball is dropped, with no limit to how far behind the bunker the ball may be dropped.
Full rule here:-
It does and you generally see good players get "steep" (more vertical shaft angle) on the backswing so they can shallow on the downswing. This isn't always the case but it's fairly typical.
Here's Rory and Adam Scott at the top of the backswing, you can see their shaft alignment is similar to mine with the top of the swing position you were referring to.
I wouldn't call these guys steep on the downswing. The shaft is starting to shallow and mid downswing (left arm parallel) their shafts will point at the ball or a little outside of it. Steep would be pointing inside ball.
Here's my early-downswing. It's moving from a more vertical position at the top to a more shallow alignment.
Steep and shallow would typically refer to shaft angle or torso/body angles.
With the above I think you are referring to upright and flat, in terms of the position of the arms? So upright would be someone like Jim Furyk or Nicklaus, flat would be Matt Kuchar or Ben Hogan. Most players are kind of a hybrid. In the swing you referenced, yes I was trying to work the arms a little more "in front of me" on the backswing.