Re: More involved than article suggests.
If you look at the pictures (and I'm not recommending you do), you'll see that many of them are taken in a mirror, with the smartphone clearly visible. In most of the ones I've seen, the phone was NOT an iPhone.
That doesn't rule out iCloud, of course - the slebs in question could have sent the pictures to iPhone users - but if many of these pics were taken on Android phones it's not entirely impossible that some Google+ hackery is going on as well...