It is exactly about rake and trail. Rake is the angle of the headtube back from the axis of forward motion along a horizontal surface - the greater the rake. the greater the vertical plane lean of the wheel when turning, and the greater the force required to control it and return the wheel to center. Think about a chopper - serious rake, and long "ape hanger" type bars. Without the lever arm those bars provide, controlled turning of a severely raked chopper fork and wheel is pretty problematic.
Trail is about the difference between the wheel center axis of rotation "trailing" the head tubes axis of rotations projected point on the ground - if, with a raked fork there is no trail, the contact point of the tire trails the axis projected point by the reciprocal of the rake angle, in a 90 degree arc. The greater the trail angle in that arc, the greater the likelihood of scrub in cornering, and the more effort it takes to turn the wheel against its own inherent gyroscopic force from rotation.
So, with springer type forks like those, unmodified straight dropouts on those straight tubes would put the contact patch with the groound AHEAD of the axis of rotation of the head tube - not good. In cases of that sort, steering "feel" is greatly decreased, steering effort is increased, and the likelihood of loss of control escalates rapidly. So, the back angled dropouts return the center of rotation of the wheel more nearly to the axis of rotation of the forks - mechanical forces are lessened, simplified, asnd more controllable.
I'd bet it turns on a dime, and gives you $.09 change, while feeling easy as can be to control.