3090 FE sli slot has different position compare to 3090 reference card

sli does work in a 4x slot but but that's really only the case where the mobo has 3 or more pci-e slots already its a driver certification

Nvidia HB SLI Bridge 4 slot

slizing hot slot SLI Bridge

slingo starburst slot CONNECTOR FEATURES · The whole length of the SLI bridge adapter is 10cm, This female to female cable has 26 pins at each that you can connect the graphics