Someone told me they used a cross platform framework to make the game, so Id guess its only on iOS because thats all they tested it on so far.
I admit, I would have gone for a html5+js option myself too though if I was developing it. I cant imagine it needs native level performance or access. So, yeah, it might be a security thing. (although, honestly, as long as the javascript is obfuscated/minified its not going to be much easier then anything else to hack). Might also just be developer preference. Go with what you know.