Yes, that is the default behavior of the embedded browser. We don't recommend checking the User Agent string or the version of the browser. Instead, use feature detection.
Also, if the page is including the X-UA-Compatible meta tag with IE=edge, the page will render in document mode using IE10/11.
For MPages 6.x, the page will render in document mode with IE10. However, there is an option to force the view to be rendered in IE11 document mode.