This is a bit of a difficult question to explain in the title but hopefully it will make more sense after reading the question.
I'm in the process of designing a web app with a basic design consisting of a continuous-scrolling content stream and a sidebar that allows the user to jump to specific points in the content stream. If the user requests to jump to a specific point in the content stream, the content area is cleared and the new content from the requested point downwards is loaded (also note that the user is able to scroll upwards to view content higher up the stream, if they've entered part-way through in this manner).
Now, if the content around the point in the content stream that the user has requested to jump to is already loaded, it would be possible to scroll directly to that point without clearing and reloading the content area, but this would mean that in some cases the user is taken directly to the content and in other cases the existing content would vanish and they would have to wait for the new content to load. Although scrolling directly to the content provides a more seamless experience, I can imagine the user becoming frustrated when the behavior seems to differ at random.
So is it better to keep the behavior consistent, even though the user may have the inconvenience of waiting when it isn't necessary, or is it better to give the user the convenience of getting straight to the requested content but then surprising them when they have to wait unexpectedly?
Note also that the sidebar indicates where the user currently is in relation to the possible "jump points" in the content stream, so if they learn that using the sidebar always incurs a wait then over time they may elect to manually scroll to nearby content to shortcut the wait with the hope that the content is already loaded.