This is more of a technical question

It appears as if there's a significant loading delay on some N64 VC games. I recently purchased a used first gen Wii (the one with Gamecube controller ports), and a few VC titles were already installed.

When starting, say, Mario Party 2, there is about a 10-15 second delay during which the N64 logo (the N cube) spins on the screen before the game starts. Kinda like this:

If the Home button on the remote is pressed after the game has started, the screen blacks out before the home menu appears. Closing the menu results in about another 5-7 second wait.

This is clearly a loading process of some kind - but what I can't figure out is why. N64 games are not particularly large or memory-intensive compared to native Wii titles. The blackout-on-home-button behavior is something I've never noticed on any other Wii or Virtual Console title, and I'd expect loading from the onboard memory to be multiple times faster than loading from disc (which doesn't have this behavior either).

Why this load delay? What's happening in the background?