根据X5论坛得到的答案是：设计如此。
腾讯真是越来越嚣张了，一家独大后用户体验都不注重了（不给程序员留活路）。
听说有个申请加入vdeo白名单的，域名验证后就可以解决默认全屏（反正我是没见过申请入口，不给钱，想进来没门。）
最终的解决办法：
将video转化为canvas，逐帧播放，不过canvas貌似最高可以达到60帧/s，不过页够用了（扯淡：玩LOL起码要150FPS左右）；
copy大神的JQ代码（原理都是相通的）如下：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
<script src="http://cdn.static.runoob.com/libs/jquery/1.10.2/jquery.min.js"></script>
<script type="text/javascript" >
function play() {
var video = $("#myVideo").get(0).play();
}
function stop() {
var video = $("#myVideo").get(0).pause();
}
$(document).ready(function () {
var video = $("#myVideo");
var _video = video.get(0);
$("#myVideo").bind("play", function () {
drawCanvas();
});
function drawBlock(context, x, y, width, height, color) {
var imageData = context.createImageData(width, height);
var pixelArray = imageData.data,
pixel = null;
for (var m = 0, length = pixelArray.length; m < length; m += 4) {
pixelArray[m] = pixelArray[m + 1] = pixelArray[m + 2] = pixelArray[m + 3] = color;
}
context.putImageData(imageData, x, y);
}
function drawCanvas() {
if (_video.paused || _video.ended) {
return;
}
var canvas = $("#canvas");
var _canvas = canvas.get(0);
var context = _canvas.getContext("2d");
context.drawImage(_video, 0, 0, 640, 360);
setTimeout(drawCanvas, 30);
}
});
</script>
</head>
<body>
<center>
<hr />
<video width="640" height="360" id="myVideo" controls>
<source src="movie.ogg" ></source>
</video>
<canvas width="640" height="360" id="canvas">
</canvas>
<button onclick="play()" >play</button><button onclick="stop()">stop</button>
<hr />
<video width="640" height="360" controls>
<source src="movie.ogg" ></source>
</video>
</center>
</body>
</html>