WOL packet from internet is a plain UDP packet. Since you’re specifying IP address on your dst-nat rule, it’s then up to routing engine to select correct L3 interface (probably some vlan interface) which should pipe the packet to correct VLAN.
Packet testing method is entirely different: it uses special L2 (MAC) packet and specifying interface (VLAN101 is L3 interface on your router, it only defines VLAN indirectly via definition of interface VLAN101) is needed because router has no other information to help with out-interface selection.