gen4 slot

Since Gen 5 should be 2x the bandwidth from gen 4, doesnt this mean that Gen5 slot x 8 equals gen 4 x 16? Maybe thats not how it works, but shouldn't above mean that when the PCIe 4.0 RTX 4090 is connected into the "halved" Gen 5.0 PCIe slot, the slot itself should be able to produce bandwidth similar to a Gen 4.0 x16 slot? pg88 slot