I am wondering if there is any difference between these two connections, I know the first case can accept default value, but my question is rather from a netlist point of view :

1. Unconnected port

module test(input clk);
endmodule

module top();
    test i_test();
endmodule

2- intentionally unconnected

module test(input clk);
endmodule

module top();
    test i_test(.clk());
endmodule

Thank you