Very interesting. I saw someone on Reddit shoot this down due to each cartridge having unique Cartridge UUIDs. As a backup tool it seems great. As a piracy thing it seems fine as long as you don’t try to play online, at least if you are using someone else’s ROMs.
On the backup page - https://migswitch.com/#/backup - it says it needs a hacked console to run the NXdumpTool to create a clone of the physical game. This seems to be a big problem for normal users who actually want to backup the game cartdriges they have.