Video window resize not working RPi3

LE runs Kodi on the framebuffer without any kind of "desktop" that you can minimise windows to, so playback always runs fullscreen.

I noticed the same running pellucid on Libreelec. Also noticed that if the video begins in the minimized top right corner using the video queue feature, it is sized correctly to begin (whole video fits in small top right window) and resizes back to full screen correctly once selected / going back to “now playing”. But after that it does not get resized again to the small window when pressing back from fullscreen as you mentioned. So it seems video window size may be able to be adjusted (if only in the one direction from small to fullscreen).