ngSrc doesn't work when loading src from Apache/PHP but does for NodeJS

Question

I'm using ngSrc on a script tag to load a video player. Because the src has dynamic content in it, I'm using a variation of the ngLoadScript directive found here.

The problem: If I place a JSON resource containing the script's src into a hardcoded file (test.json) and serve the file using a NodeJS server, the script loads fine and I see the video. If I serve that exact same file using PHP/Apache, the ngSrc is not evaluated and the script tag never gets a src. The only difference between the two files' headers are the cache-control (1209600 on Apache, 0 on node), the Etag, the server and keep-alive (absent for Node, max=95,timeout=5 for Apache).

The script tag:

<script language="JavaScript" type="text/javascript-in-template" ng-src="{{getTrustedLink(details.kvLink)}}"></script>

The controller:

.controller("LearnCtrl",["$scope","$http",function($scope,$http){
    $http.get("test.json").success(function(data){
        $scope.details=data;
        $scope.linkId=data.link.substring(data.link.indexOf('embed/')+6,data.link.indexOf(".js"));
    })
}]);

test.json {"link":"https://s3.amazonaws.com/watch.knowledgevision.com/embed/9f44296925ea4e13b3a0780c31a363a1.js?Expires=2145910800&AWSAccessKeyId=AKIAIBXQ24MXQ4CMI74A&Signature=3hvr483veuUGNuQZ65RSSLhe6NE%3D"}

Any ideas why the script tag never gets a src when the data comes from a Node vs an Apache server?