Entire Screen UI is skewed

The entire UI seems to have a left and top margin however no bottom and right margin, This issue is easily replicated.

Create a new UI widget and create a div with a background colour that is full width (100vw) and full height (100vh) and you can see there is a margin on the top and left of the UI but not one on the right and bottom. Strangely if you change these units to 100% & 100% you get a uniform margin all the way around.

Im not sure what is going on here but personally I would prefer it so that when I ask for the full viewport width and height I get the full screen with no margins and when I just ask for 100% I get the nice safety margins. I came across this when trying to make a game entirely out of UI widgets blocking the 3d world from view with a full widget however this is made impossible with this bug

As standard, <body> tags always have a bit of margin and padding; adding this to your CSS will remove it all:

body {
    margin: 0;
    padding: 0;

Will look at getting those added in by default