I would think that both iOS webview and safari actually supports the same audio formats (last time I checked, apple did not implement support for the ogg vorbis format in safari, and so I would expect that for the same reason of them, they would not support it either in the webview), and the same with android webview and chrome for android(but I think chrome supports both ogg vorbis and m4a, others would confirm or deceive that I think).
The browser does, but there seems to be a conflict somewhere between C2's HTML5 Web export and CJS's 2.1 Webview+ implementation.
I see in Xcode6.1 debug, audio calls only ever seeks to load the M4A file and not the Ogg file. This is why when I delete the M4A it never plays sounds.
The reason I keep Ogg is that it works fine on Intel XDK and CJS Canvas+ for iOS. Now I'll just keep Ogg for Android and M4A for Webview+ its not a problem anymore.