So I made a bit of progress on this, if you right click and then you have the option of playing the video in a seperate window (which can be made fullscreen) or directly fullscreen but I dont like that you have to right click it, if it took me this long to figure it out no one will ever bother to full screen the video
they will just see the button"doesn't work" and move on.
Open your video in Acrobat Pro and select it with the Select Object tool, then choose properties. Regardless of what the skin says, the only two Playback Styles available for video in a PDF file are Play Content in Floating Window and Play Content on Page. There is no option to make the video full screen by default. Your workaround is the only way I know of.