I think you need to start a new project to reproduce the problem.
If I load the netlist using 5.0, save and reopen using the master branch then new footprints are added.
But if the board is empty and I load the netlist using the master branch then nothing is added.
I noticed that m_Modules is empty in pcbnew/class_board.cpp:2571 and the modules are added in that loop.
I think you need to start a new project to reproduce the problem.
If I load the netlist using 5.0, save and reopen using the master branch then new footprints are added.
But if the board is empty and I load the netlist using the master branch then nothing is added.
I noticed that m_Modules is empty in pcbnew/ class_board. cpp:2571 and the modules are added in that loop.