This is expected and logical behaviour: The energy originating from the Huawai will immediately cover any consumption there is, and only the remaining (unused) energy will become visible at the grid.
Thus, the Victron-System has no indication to know, if there is:
2000W Solarproduction and 0 consumption, or
4000W Solarproduction and 2000W consumption.
To fix this, you need to explicit tell the Victron System about the added Solar-Production, then it could conclude the real consumption:
If the Huawai supports Modbus TCP (Sunspec) it as easy as adding it through the PVInverter Integration in the gx, after enabling the Modubus TCP Endpoint on the Inverter.
If it does not support that, you could add a dedicated meter in front of the Huawai inverter and add this as Role PVInverter to the gx. This won’t give you all the details Modbus TCP could, but it will satisfy the need of knowing about additional Solar-Production, allowing to calculate all other figures correctly.