I just timed Breath of the Wild (cartridge version), and from the time I launched the game from the Switch menu to seeing the game menu was about 16 seconds, and the time from selecting a save file to loading the game world was about 18 seconds. What exactly about this game makes it take so long to load?
They did this by overclocking the Switch during load. I didn't see any mention of boost/overclock in the Factorio writeup, though.
I found a GameFaqs forum thread[1] from shortly after the game launched that claims it was about 20 seconds. And a US Gamer article[2] that says the update that came a couple years later only shaved off about 5 seconds (seems within the ballpark of what I measured)
[1] https://gamefaqs.gamespot.com/boards/189707-the-legend-of-ze...
[2] https://www.usgamer.net/articles/breath-of-the-wild-load-tim...
Perhaps they don't get to mess with the clock "willy nilly" and it's more like an API that enables a higher - but fixed - clock speed?
[1] https://www.shacknews.com/article/112895/crash-team-racing-n...
It overclocks the CPU at the expense of GPU. It's suitable only for loading screens or other areas of the game where you don't need to render at more than single-digit FPS, but can produce a 20-50% improvement in loading time.