Let's look closer into memories. In the video excerpt from Harry Potter and the Goblet of Fire we have seen what we might call a trip into the past. The protagonist sees with his own eyes some events that have taken place years before. This is achieved by means of a magic device, not by some recording technology, but either way, the way the protagonist comes to witness those past events resembles a kind of highly sophisticated, multisensory holographic film playback. More interestingly, we immediately realize that we're looking at past events that are in some way recounted. We understand, at the latest when we hear Dumbledore's explanatory comment, that we have just re-experienced an episode out of his memory.
So far, so good: the scene has served its function. However, if you think about it for a moment, you'll notice that appearances notwithstanding, all this is in fact very different from memories as they work in our lives.
When you remember an episode from your past, normally you won't go through the whole sequence in minute detail. If it is a vivid memory, then you'll probably have no difficulty to invoke the mood, the general feelings you had; you're probably also able to make some key images or sounds present again in a kind of sensual way (that is, you'll see them with your mind's eye, or hear them with your inner ears); and you'll be clearly aware of spoken words and sentences, though very likely again not all of them, but some that stand out for you in your recall. For me, one of the strongest memories I have is of a particular concert given ten years ago by a violinist I admire; it was the first opportunity for me to listen to her playing live, and I can recall clearly many of the details: the way the room looked, the row in which I was seated, the setup of the stage, the orchestra, the acoustic impression I had, the excitement I felt, the way the music affected me. And yet of course when I recall this experience, I don't go through the whole of the concert, movement by movement, in sequence and in tempo. What I recall are the feeling, the general flair, and several key impressions.
If that is how memories usually work, then why can we still understand what the film wants to express (namely, that Harry has just lived through one of Dumbledore's memories)? It's because there is something of which it reminds us. But that is not a typical memory, but recounting a memory, more precisely, the recounting of a memory for the benefit of someone else who wasn't there. When I'm not just recalling a past episode for myself, but want to relate it to someone in order to help him imagine what it must have been like to have been there, then what I do must be more structured and more detailed than simply recalling the feeling, the general flair, and several key impressions. What we do then is to tell a story. We describe the surroundings; we point out the key characters, their look, words, and actions; we narrate the events in a certain order that leaves out the unimportant ones but brings the important ones into an intelligible sequence.
So what the scene in Dumbledore's office resembles is not recalling a memory, but recounting a memory in dramatized form. It's not as if Dumbledore would remember, but as if Dumbledore narrates what he can remember. The past events are brought into a story-like structure for the benefit of a listener. (Or, in fact, for both a listener and us, the audience.) True, the job is done not by Dumbledore himself but by a magical device (the Pensieve). But the structure is still the structure of telling-it-to-someone-else, not the structure of simply remembering.
Consider this: a classical flashback would have served the exact same function. We can easily imagine Dumbledore and Harry sitting in the office, with Dumbledore saying something like: "I still clearly remember, it was a few months after the war, when we were all convened at the ministry...", and then blending over into the scene of the hearing. In that case, it would have been easier to detect that we're not simply witnessing the process of remembering, but the structured and dramatized recounting of a past scene. (There is of course a reason why the magical device is used instead of a classical flashback: the Pensieve has some role to play later on in the plot, and it's introduced here in preparation of that later role.)
Thus passage into memories (as a variety of a past world) will be rather passage into a narrated version of those memories; memories themselves are too unstructured to constitute a proper destination location. (Compare this with dream worlds, which are also strictly speaking to unstable to make a good destination, but are prepared by fiction that features passage into them in a manner that addresses this difficulty; I have discussed this in an earlier post.)