In a well-constructed joke, everything before the punchline provides context (called "setup") for making the punchline funny; nothing should be extraneous.

Analogously, the author could treat the lilfe-as-normal start the same way – the goal is to get to the PE, and everything before that should be only what is needed to appreciate the PE. Perhaps the author rushes to the PE, or perhaps the author proceeds at a normal writerly pace, but the goal is clearly in mind.

Some authors detour, no doubt with the goal of having an interesting start.

The PE is the main character getting rejected by all of the colleges she applied to. The scene of her mother driving her to school and having car problems delays getting to the PE. Meanwhile, it provided little if any context for the PE. So, that scene seems to be placed in that book just to be interesting.

The scene is interesting. It shows character. It's a slow reveal of setting. The only problem is its placement – it's a detour

Another Example

From Gone, by Kellerman.

Describing a character is a standard technique to try to make a character "come alive" so that the reader cares about the character, and hence cares whether or not he dies in this scene.

But it was a serious detour in getting the story started, especially as the character doesn't appear again in the book. And the scene does well without context – it's interesting that a naked woman runs in front of him. If Charley's living or dying is important, that works well without context too.

I did not fault the slow start in The Winter of Our Discontent, which in its meandering way mostly told us what we needed to know. I did not fault The Princess Diaries. Those authors kept the goal in mind, they just moved slowly towards it. The above two books could have some clever plan I don't see, but it seems more like the author got distracted.

Borderline Meandering

Ender's Game begins with the PE, him being selected to attend Battle School. They take out a monitor out of his brain, that feels different, when he goes to school the other boys bully him, and Ender has to deal with that.

Anyway, as his monitor is taken out, Ender almost dies from the shock. That has nothing to do with the story, as far as I can tell. It of course adds drama to that first scene. But it was a detour. (Card is the only author I am afraid to criticize – he's that good. I am not even saying his choice was wrong, but it was a meander.)

Wicked Appetite begins with a description of the main character. She is called beak-nose in school, because of the shape of her nose, but she breaks it as a young adult, and now she has a cute nose.

Why spend time discussing a nose she does not have? And, remember, this is fictio – why was that even added to the story? Maybe there is some reason I cannot see, but the goal seems to be adding something exciting to a description. But it's a detour.