"Before any of the numbers: what is the angle measuring?"
Four real receptions, one per band. Every dot is a measured joint from the pose file at the frame the ball reached him, drawn relative to his own hips. The thick green line is his shoulders, the dashed line is the direction of the goal he is attacking, and the angle between them on the ground is the only number this study uses. Drag the left panel to turn it.
"Is he already open, or does he have to turn?"
One column per 15° band. 0° is square to the opponent's goal, 90° is side-on, beyond 90° his shoulders point back towards his own goal.
Measured from the receiver: a feed at 90° is the square ball across the back line, a feed near 0° came from a team-mate further up the pitch playing it back. The condition that the whole opposition is in front of him is not a filter we had to force: in deep build-up it is simply true.
"Open means he carries or plays forward. Closed means it goes backwards."
If pressure were doing the work, the gap would shrink in the pressed row. It widens.
Least squares. The shoulder angle and where the ball came from both separate from zero; pressure, depth and the length of the feed do not.
A look away from the ball means his head more than 60° off it for at least 0.2 s, in the three seconds before it reaches him.