Outa loop here: Nintendo used third party rom dumps for their own first party services ?

They've even been caught yoinking emulator code.

The 2020 gigaleak proved that they still keep old source code and assets, and they still need to pirate their own roms?

That was a theory but I’m quite certain they had people working on it in house.

https://nintendo.fandom.com/wiki/Tomohiro_Kawase

Need is probably a strong word. Why bother working through a proper port when you can port a single emulator and sell dozens of your own pirated games?

Their original Virtual Console NES games on the Wii had the roms extracted from them, and they were found to have ROM header data matching how the emulation community formatted it, with files set up the same way as online communities did things. Theoretically they could have put that there themselves so their in-house made emulator followed the conventions of open source ones, but people think it's more likely they just downloaded the ROMs from the internet and they came that way.

Emulators and firmware blobs are about as far apart from each other as trees and hippopotamus. You need the firmware blob for the emulator to work, but I highly doubt Nintendo just had a source code repo of emulating an n64 hardware system on x86-64.