I noticed that I got answers System Product Name and To be filled by O.E.M. only from local agents:
If I use installed agents, then I can get more detailed information. In my networks a lot of different agents from 2.0.4 to 188.8.131.52. In some networks I have no right to install agents, so I have to use Local Inventory and then Import these files to the server.
But correct me if I'm wrong there is no differense in report file when I use Network Inventory or Local Inventory.