From Microsoft's official "Microsoft on the Issues" Blog:

It seems to us that Google’s reasons for blocking our app are manufactured so that we can’t give our users the same experience Android and iPhone users are getting. The roadblocks Google has set up are impossible to overcome, and they know it.

It's ok to have an open API, and it's ok to not have an open API so that your competitors can't benefit from your services, but claiming to have an open API and then shutting out users of a competitors platforms on a string of technicalities? That's just a joke.