So to continue my flawed analogy, a storyboard is going to have way more "pages" than a graphic novel of the same material would?

Way more. Every time you see a cut in a movie, there's a frame of storyboard.

But, if you feel like answering another question, how do you decide which shot gets a storyboard frame?

Simple. Every single goddamn one.

Surely you can't account for every single different frame of a movie, too labor intensive.

No, but you get every single shot. As in, every single time we put the camera somewhere else, every single time we roll and then cut.

I don't think the White People Edition has it, but the Chinese and Japanese DVDs for Spirited Away include an alternate video track - the animatics of the film. That's the storyboards, timed out and presented as video. It was kinda trippy when I saw it, because my Chinese DVD defaulted to video track 2 for some reason. I thought it was a decidedly low-fi Miyazaki, but still pretty cool. I had to watch the first 20 minutes over again when I figured it out.