Sure it does. Allowing windows to draw their own decorations, often in different ways and with different styles and themes, and not respecting the settings in xfwm4 as to what window-control buttons should be drawn (and where)... that's a huge UX issue.
The process drawing it's own decorations? Technical decision that both Windows (tad complicated) and macOS already do, nothing to do with UX. There's nothing stopping this model from having the uniformity of SSD (as like on macOS), but it does on Linux due to multiple toolkits which don't all agree with eachother.
Sure it does. Allowing windows to draw their own decorations, often in different ways and with different styles and themes, and not respecting the settings in xfwm4 as to what window-control buttons should be drawn (and where)... that's a huge UX issue.