I can't say for certain that's the case, but:
• If true, it's a really fucked up UI/UX. Because the two actions have absolutely no need to be associated.
• If not true, it's a really fucked up UI/UX. Because in two years of using photos, I haven't sorted it out, and I routinely see people sharing individual photos to their streams (I occasionally ask "context") to find that they're assembling an album of some sort.
Again: the photo-sharing is pretty much useless on account of that, and Imgur shines by comparison.
If you want persistent storage you control, buy an S3 share or host your own. Frankly, broadband access is to the point the latter is viable for personal accounts. I'd like to see some sort of P2P distributed cache which shares load as well.