Didn't the 3DS take forever to get a decent emulator?
Most likely because of the very different GPU and API, i think.
Tegra is well known hardware, and both GPU's from Switch and Wii U are close to the PC-hardware, Nvidia and AMD built. The CPU's are far from the nightmare CELL was.
It's also very likely that both system architectures make a less acurate, thuogh faster emulation relatively simple.
If you look elsewhere, it can be difficult to get a decent emulation of even pretty old hardware. Sega Saturn has always been a nightmare foremulator devs and is far from perfect until today.
Even emulators like Dolphin still have many issues, usually because of parts of the hardware.
Going for more standard components makes emulation way easier.