Radial Gradient issue

Radial gradients are always circular. If you start with a simple Ellipse with a gradient fill, delete the default stroke, Group the Ellipse, then add a couple of expressions to control the end point of a gradient and calculate the ratio of the horizontal and vertical dimensions of an Ellipse to modify the Transform/Ellipse/Scale value and add a Stroke to the Group you can get a shape layer with a circular gradient you can control. You will also need to unlink the Size parameter to change just the Y value to make the oval. The Transform Gradient 1/Scale expression reshapes the oval Ellipse to a round one. The Gradient Fill/End expression ties the end point of the gradient to the right edge of the ellipse, and the Stroke added to the Group keeps scale values from distorting the stroked path.

Here are the expressions:

// Gradient Fill End Position
[content("Group 1").content("Ellipse 1").content("Ellipse Path 1").size[0]/2, 0]

//Transform Ellipse 1/Scale;
r = content("Group 1").content("Ellipse 1").content("Ellipse Path 1").size;
[value[0], r[0]/r[1] * 100]

  Here is it at the extreme:

To rotate the gradient, all you have to do is edit the Transform Ellipse 1/Rotation property.