Hi Felix  unlike a circle the ellipse from center point takes points for where to place both its horizontal (corresponds to width entered) and vertical (corresponds to height entered) axis points.
So until you are at the stage of placing the second axis point, only a line will be drawn from the center to the first axis point.
The command does not yet have all its information that it wants to make an ellipse until you are at the stage of picking the 2nd axis point.
The click for setting the 2nd axis is kind of redundant when width and height are given when you are only working in a 2D viewport like only drawing in the Top view, but you can see a bit more clearly how it works if you place the last point somewhere in 3D  that orients the ellipse. For example try drawing an ellipse in the 3D viewport and for the last axis pick a point using z snap upwards, you'll see the ellipse turns upwards then.
That is correct that it is different than drawing a circle. Basically the difference comes from the process of how things work when you do not enter in any numeric values. When clicking points only, a circle picks a center point and then a radius point, while the ellipse picks a center point, an x axis point, and then a y axis point for the ellipse.
When you enter in numeric values they behave a bit differently  the circle finishes immediately when you enter in a numeric value, but the ellipse command still asks you to pick the same points that you would use if you had not entered numeric values  that's because a circle has a sort of uniform symmetry about it so that it doesn't make much difference which direction its x axis is pointing inside of its plane, so it just makes its x axis point in a default direction when you enter a radius value numerically.
 Michael
