The ig-platform-id didn't really match with what you said. The SMBIOS seems to have changed properly. But the graphics are only in VESA mode.
I'm using OpenCore Configurator and the settings I had under DeviceProperties were,
AAPL,ig-platform-id - DATA - 09001659
device-id - DATA - 16590000
I changed to,
AAPL,ig-platform-id - DATA - 09001619
device-id - DATA - 16190000
Is it correct?