Internet Explorer 11 and <iframe> document mode inheritance

Situation:

I have a site that is loading to another system inside <frame>

that is disabled. In my page I set IE to install the latest version: <meta http-equiv="X-UA-Compatible" content="IE=edge">

. When it opens on its own, the site looks great and the web inspector tells me that it is in Edge mode.

When I open a site inside another system, the web inspector tells me that the default mode is 7 , and it is set because via the X-UA compatible HTTP header: This is also because the server is sending the HTTP response header X-UA-Compatible, IE=EmulateIE7

.

The frames.aspx page containing <frameset>

and <frame>

already has an HTML5 DOCTYPE declared, but no X-UA tag <meta>

.

Question:

I thought the X-UA tag <meta>

inside my site would overwrite the server response header .... Or is it because the frames.aspx page does not contain an X-UA tag <meta>

, so IE7 mode is set on that parent page (via the HTTP header answer), then it is inherited before my site?

Would love to hear any thoughts about this situation.