They don't come with a free Office 365 account, they come with Office Mobile 15, which is version Office 2013 basically. It's a simple Office suite for Word document creation/light editing/viewing, PowerPoint creation/light editing/viewing, and Excel creation, you get the gist.
If you bought the standalone 2013 Office suite, you will need to buy 365 for ios. Those are two different SKUs.
But Office on Windows Phone is baked in, free to use without subscriptions or anything. Think of it as how Microsoft bundles in Office Home and Student for baby sized tablets.
Ok, but there is no Office for iOS, they are free apps, but only work with an office 365 prescription. The only change was the release of the Word app for iOS, but that also is Office 365 only.
But you are saying, you CAN edit, Print and Open then, with the built in Office Suite on a WP... THAT sounds a lot better. So, Microsoft in other words does what Apple does with iOS 7 now, by including free access to a full working "Office" suite - They used to call those apps "At Work" or maybe iWork. But now they each have their own area in iCloud.com, and what I like about it, is if I start a Doc in Pages, I can resume editing on any Mac or PC Desktop via any browser and iCloud.com. Apple made sure there is full Office compatibility, you can save any pages doc as a Word docx file. If Microsoft does the same thing for any docs you create in Office for WP, then that is a great thing.
I've never had any trouble cross platforming between OSX iOS or any MS OS.