This is the way Chuck Ahrens used to overhead press back in the '50s. Instead of pressing the dumbbells straight overhead, he'd press them up and out. At the top, his arms and head would form a "W" shape.
The reason he did overhead presses this way was simply because he used special dumbbells to accommodate the amount of weight he was lifting. Those dumbbells were wider than normal, so he had to press out to avoid them colliding against each other.
Ahrens is likely among the strongest men in history when it comes to pressing overhead, using 170-200 pound dumbbells for standing strict dumbbell presses. And he did that for reps. Keep in mind this was in the mid-1950s; steroids weren't used back then.
I recently started having my athletes use the Ahrens press. For them, it's meant to specifically improve the catch position of a snatch, but as a by-product it's had a positive impact on delt strength and size.
This pressing variation is great at improving shoulder stability and medial delt development leading to more width. It also takes some of the load away from the triceps and upper pecs, so it's more delt-dominant than regular overhead pressing.
You can do it seated or standing. In both cases, focus on trying to reach "out and up" at the top to maximize contraction and muscle growth.