I'm pretty sure that's just a remnant of a 3090 PCB design that was adapted into a 4090 PCB design by the vendor. None of the cards based on the AD102 chip have functional NVLink, not even the expensive A6000 Ada workstation card or the datacenter L40 accelerator, so there's no reason to think NVLink is present on the silicon anymore below the flagship GA100/GH100 chips.