This will only work on lever handle doors

Pushing directly against the door might break the handle or the door, so it’s better to redirect the force downward, and then, after the handle has reached its limit, push the door forward.

Trying to muscle through a door would require a lot of strength and could potentially injure someone who is not strong enough, like a weak, elderly person. It also requires a lot of muscle, leaving very little for the downward push, resulting in a big loss of force.

Therefore, it’s more efficient to push the handle down before pushing forward, which requires less muscle and reduces the risk of injury.