Mackenzie, it's not a workaround for plymouth not quitting properly on starting gdm, it's the code that's necessary to provide a smooth, flicker-free transition from plymouth to X. To get the same flicker-free behavior on Kubuntu, similar handling will need to be implemented in kdm, but the current buggy behavior is orthogonal to this - plymouth itself is misbehaving when stopping on kdm start.
Mackenzie, it's not a workaround for plymouth not quitting properly on starting gdm, it's the code that's necessary to provide a smooth, flicker-free transition from plymouth to X. To get the same flicker-free behavior on Kubuntu, similar handling will need to be implemented in kdm, but the current buggy behavior is orthogonal to this - plymouth itself is misbehaving when stopping on kdm start.