Here are two comparison pictures of the stock and Whiteline ball joints:
Difficult to compare, but at least at first glance, they don't appear to be that different. I would expect that the Whiteline ball joint's shank would be about 1" longer, figuring that most cars are lowered at least that amount. It looks like the location of the center of the ball joint is different relative to the LCA. If this is the case, then this product would do nothing to correct the roll center, based on the following article:
TLDR? Here's the essence:
"The roll center is located by first finding the front view instant center of each side of a car’s suspension. The instant center is the point in space that the suspension’s links will rotate around. Drawing lines from the center of the ball joint
[my emphasis] through the inner pivots of the upper and lower control arms and extending them inward towards the center of the car until they meet will let you locate the instant centers. Now draw a line from the center of the tire’s contact patch to the instant center on both sides of the car. The point where these two lines intersect is the roll center. For a car with McPherson strut suspension, the upper line is found by drawing a line 90 degrees from the strut axis starting at the upper mounting point of the strut."
It looks to me like the center of the Whiteline ball joint is in the same location as stock relative to the inner pivot, only the angle of the LCA has changed. But in effect, only the shape of the LCA has changed, effectively inserting a dogleg 90 deg angle in its shape.