Monolith has also been helping Nintendo's main EAD teams ever since Skyward Sword back in 2011. They probably should have been loaned out to Koei-Tecmo for Age of Calamity, but yeah this is likely why BotW was able to maintain a stable FPS through most of the game (Lost Woods being the notable exception), and why BotW2 looks so good that Digital Foundry is questioning if the game we're seeing is even running on now half a decade old hardware.

And then you play them on an emulator and upscale to 4K and add a 60fps mod.