A grid tied inverter is usually controlled so that the generated power (e.g. of a solar panel or a wind turbine) is completely supplied to the grid. The grid impedance can be expected much lower than Vgrid/Iinverter. In so far, ohms law doesn't apply.
An inverter which is operating as a controlled AC voltage source, e.g. a H-bridge with voltage bus, needs a coupling impedance to the grid to be able to control the output current. In most practical cases, a series inductance is playing this role.
The linked paper assumes a high Q 50 Hz resonant circuit as coupling element between inverter and grid. This might work in theory but is a rather unrealistic idea related to real inverter designs. The supposed 4A 100 mH inductor is huge related to the small inverter power.