It also appears if you somehow end up with a positive balance (e.g by receiving a red packet). I haven't tested whether you can actually spend that balance without having linked a Chinese bank account, though.
I have tested the red pockets but I couldn't actually receive them. It's been year back or so.
Yeah I could see the incoming red packet but i couldn't accept it, Eventually the transaction just voided itself. This was 6-8 months ago.