I want to update my answer.
The default configuration changes in the PCIe router when there are supported SPF+ modules present.
- Without supported modules the PCIe passthrough devices are on a bridge together, and are disabled.
- With Supported modules the PCIe passthrough defaults to having SFP28-1 and SFP28-2 passed through in their own PCIe virtual devices and the other 2 virtual devices as management port passthrough just as described on the product page in the diagram.
In my case I disabled the virtual PCIe device passthrough and the ports are all dedicated to the router. My host system still sees the PCIe devices however they show up as not functional and un-configurable.
It seems that the virtual PCIe interfaces are hard coded, although my testing has been limited.