@johnandmegh, actually, in this case, Spectacle is capturing exactly what’s rendered. When I tile a window to an edge, I see the window border wrap around the title bar, then stop at the window content, as depicted in the screenshots. I expect that this is a bug in the Breeze KWin SSDs. 
Thanks for linking that issue, though, because I’ve encountered that too, and that saves me reporting it myself. x