@neauoire
Window origin is top left.
Most (right handed) people would resize bottom right. Some UIs even have resize handles there. Pre-composition area, resizing bottom right also had the smallest redraw impact, with fewer pixels to redraw in the buffer. It feels natural to me to have the scrollbars meet in that corner.
Origin would work...
But consider that auto-toggled scrollbars would let the content jump.
So, I guess the scroll bars are bottom right because we start reading top left.