I don't see how they could have hooked a 2.5Gb/s Ethernet NIC to the CM4 modules without using up the single PCI-e 2.0 lane other than adding a power hungry, ex

I don't see how they could have hooked a 2.5Gb/s Ethernet NIC to the CM4 modules without using up the single PCI-e 2.0 lane other than adding a power hungry, expensive and often out of stock PCI-e switching chip.