Actually, primetime already feels like a highlights show. The sports that are run in primetime, all of them are filled with side stories and the actual events are reduced to show American athletes (and I do want them to show American athletes) but they cut a majority of the action that is going on with non american athletes. The problem with your argument is that you assume NBC is full of first run events in primetime when they are not. They are full of tape edited, not showing the whole spectrum of the games.
Yes, that's still first run when you haven't seen the video yet, even if you know the results. This isn't a football game or a golf tournament. A 2-minute swim race where you know the results is a lot different than a 3-hour football game that you knew the final score to. That's why I'm saying you can't show everything earlier and then repeat it in primetime because then it's no longer first run. And if you think primetime is already a highlights show (which in some ways it is), then what's to change about it? They have to edit it down somehow. There's a lot of dead time during Olympic events, so that editing almost helps to make it more compelling, even if it cuts out a lot of competitors. But again, if you want these events in full (and you get them largely without interruption), you have that option now. That's how you satisfy both fanbases.. those who want constant action and those who are in it for the storylines.
But you may say, well, this is already been done with the online coverage. But you see, the online coverage does not give you the ultimate experience. The current online coverage is a feed with no commentaries (not that I like some of these commentaries, but you still need someone to run the show, it's like having a party with no DJ). One can also make the argument that the online feed is not as appealing and practical in terms of the HD viewing experience as watching television channel. Although people are capable of turning their computer into a 65 inch HD display in decent quality, there are several things that the end user will need to be ready for in order to accomplish that. So it is not a practical idea when there are millions of fans.
That's the whole point though.. NBC thinks (and I'm planning on doing this myself) that you'll watch the live feed and because it lacks context, you'll check it out again in primetime.
You have to remember.. NBC's goal is to get you to consume as much of the Olympics as possible. If they're showing their best stuff in the afternoon, is there going to be a draw to see a highlights show in primetime? I don't see it. Besides, you don't want people to skip over the qualifying rounds and go straight to the finals. How many people want to watch all of the Phelps races, not just when he goes for medals. Setting up a specialty channel is only going to detract from what you already have, not add to it. If you're trying to maximize the total number of hours of Olympics coverage consumed (let alone the business side of things of trying to generate advertising revenue), I don't see this being able to increase that and if anything, you're hurting it if you're encouraging people just to watch finals and have the best stuff done with by the end of the afternoon. Because after that, they'll be seeking out something else to watch, not watching the highlights (which is to say the re-run) in primetime.