YouTube is always buffering/streaming whether in full screen or not. Whenever you reload the video (either by pressing play again, refreshing, or going into full screen), the video will rebuffer.
Hmm. I get that it rebuffers when refreshing or going fullscreen, but I haven't noticed any rebuffer when I click play again. Multiple times I've lost my connection while a video was fully loaded and hit replay, with no internet connection, and it replayed the video.
Thanks for the response!