We do not recommend trying system transfers at this time. When you do a system transfer the console also tries to contact the servers to move data over. This easily causes desyncs in what data your console has and what data our servers have, especially if you do a system transfer where at least one console is connected to Nintendo’s servers (like in your case, with an unmodded console), since that data transfer is completely invisible to us.
It’s somewhere we’re aware of and want to support in the future, but right now there’s just a lot of roadblocks.