Are you absolutely sure that this is a statement of fact or it is an opinion???....
Tom Watson had a lot of elbow bend and his plane angle wasn't shaloow...He shalllowed it out by a full sweep release and an increasing the amount of Axis Tilt...
As a matter of fact if you maintain too much right elbow bend it is difficult to get the right forearm pointing at the plane line during release and impact....
It's opinion not fact, I'm just generalising. But remember I'm assuming that the Right Forearm is On Plane (as it should be), not above or below Plane, as a few of your photos show.