How does the new “download additional fonts” feature works？

I'm so happy to see that the “download additional fonts” feature has added in the newest iWork suite for iOS. In previous versions of iWork for iOS, available fonts are only limited to those that iOS has built in, which you can see a complete font list here: iOS 7: Font list.

And a couple of days ago, I found that the iOS 7 is now support “download additional fonts for Apps” feature. Which means that Apps can download a Apple-provided list of addtional fonts if necessary. And we can find this list of font in that support page given above.

So if you edit a pages / keynote / numbers file on a Mac using some fonts that iOS hasn't, then when you open it on an iOS device, it'll download the fonts for you to make your document more beautiful and personalized. That is to make sure that the document has exactly the appearance that you wanted.

But here comes the question:

1. Sometimes, those addtional downloaded fonts are available for all the documents in that App, and sometime they are only available on that particular document. Any idea how does this function work? Is it a normal function, or is it a bug waiting to be fixed?
2. The downloaded "addtional fonts" are only limited to that App you're using. For example, you can access the fonts in which the App you downloaded them. So if you're using Pages to download fonts, you won't be able use them in Keynote. In other words, you have to download them again, and this will obviously take a large amount of storage space on my device if I want to use those fonts in every App. So again, is it a normal function, or is it a bug?

Any solutions, guys? A thousand thanks in advance!