I just tried die another day, region 1, with clonedvd sneake preview a picked angle one only (movie only) but I notice that angle 2 remain there, is this a bug? I double tried to may sure and same results.
Thank your for your report Tigger00, this was very helpful! I can confirm that this is a bug in the CloneDVD2 Sneak Preview.
Note: angles are never removed logically, but the video-parts specific to the unselected angles are expected to be replaced by black frames.