Leakage Current in a AC/DC PSU without earth?
If you look at the datasheet block diagram, there is a capacitor between mains input block and isolated DC output. It is there for EMI suppression. Also even if it was not there, there would be stray capacitance over the transformer coils that can leak AC voltages. Oh and forgot to mention, mains voltage is usually referenced to earth as neutral and earth are connected at some point anyway.