As Adobe help reports :
Applications: and storage application: schemes are not supported.
On iOS, your code works fine, but on Android you have to achieve this with some hacker implementation like yours because there are security issues related to loading StateWebView URLs from these directories. Another solution is to copy your application: or the storage application: the file to a temporary one and load this temporary file into StageWebView:
var htmlFile:File = File.applicationDirectory.resolvePath(url);
var workingFile:File = File.createTempFile();
htmlFile.copyTo(workingFile, true);
stageWebView.loadURL(workingFile.url);
: , html- .as StageWebView.loadString(). , Android.