I'm not even going to go into the relevance of touch-enabled devices for a Linux desktop but this is awful even by general standards. The clip problems list is laid down vertically, so pointer movement is primarily on the vertical direction. Even if you don't go through the list, you'll usually go over the window vertically just to get to OK/Abort or one of the buttons in the uperr-right section. Whatever ID gains (in the sense of Fitts' law) one hopes to gain by making the widgets fatter are more than offset by the increase in travel distance due to widget stacking. You get targets that are harder to hit and extra scrolling.
This is a good trade-off on a 6" touch screen, where you're gonna do a lot of scrolling anyway so you get to work on the one factor you can control (pointer resolution), especially as pointer motion isn't constrained to a single plane (thumbs move on the vertical axis, too -- in fact even easier, due to anatomical constraints). I'm gonna go on a limb and say that I suspect the vast majority Plasma users are running laptops and desktops with screens slightly bigger than that and either a trackpad or a mouse.