Well, I think you’ll see from more recent posts that the open/shared aspect is for annotation. But yes, that’s a very difficult thing to do without adjacent frames (a starfield would be impossible).
And certainly for actual cleaning you need surrounding frames. PFclean’s spacial predictions are surprisingly clever, but the real power comes from temporal patching. Plus, as I’m sure you know, having the entire shot allows you apply other tools like deflicker, etc.