I agree that there is a subtle difference between using rear tilt/swing and tilting the easel (or its digital equivalent of using perspective transformation in Photoshop), but I don't think that the difference is in the rendering of the relative size and shape of objects in the frame. Either method can be used to correct convergence in one plane in the image.
Rear tilt/swing or easel tilt alone will not correct a complex composition with multiple planes at multiple distances, which is best corrected with rise/fall of either standard on the camera, and post-processing methods will have no effect on the plane of focus in the image.
The advantage of applying rear tilt/swing in the camera over doing it after the fact is that it can be done without the loss of image quality that would result from varying the enlargement factor across the frame, and without the need for cropping the trapezoidal image that results. Doing it in the camera also eliminates the need for stopping down the enlarging lens to compensate for the easel tilt on enlargers that lack a tilting lens stage.
That said, the kinds of corrections usually applied in the darkroom are typically small, and for small corrections, easel tilt is quite effective.