The math doesn't work that way Paul. I am going to use my X370 board, it's AMD but the science behind it is pretty much the same.
My 1700 has 24 PCIe 3.0 Lanes coming from the CPU. I have 2 NVME/SATA M.2 ports and 8 Sata ports. 4 of those PCIe lanes go to the Chipset. The board/chipset then take the 4x PCIe, splits it down to 8x PCIe 2.0. 4 of those go to one of the M.2 ports that is shared with a PCIE 4x slot, 1 goes to a PCIE 2.0 1x slot, the other 3 get split out for USB/Sata/Audio and other extraneous items (like my boards add-on asmedia 2 Sata ports).
4 PCIE 3.0 lanes goes to the primary M.2 slot. The other 16x goes to Primary PCIe 16x slot and then split to secondary slot if both have something installed.
The reason I point this out is that the M.2 slots both support Sata. But both are dedicated connections shared with respective SATA ports. Having Sata enabled doesn't steal away performance. The slot just happens to be wired for it. For the first slot if PCIe 4x is used the sata one is untouched. If SATA is used the 4x PCIE goes to waste. For the second slot, same thing, but one difference. If PCIe drive is used a 4x PCIe slot is disabled. If SATA is used a sata port on the board is disabled. SATA just happens to be another tech using the the 4x PCIe assigned to the chipset, used as needed when needed. The resources that the chipset sets aside for these non PCIe workloads (USB/Audio/Sata) can't be reassigned. They are just there to be used when needed.
The Intel platforms work the same way but they a multiplexer in the chipset that takes the 4x PCIe lanes in for communication to the CPU, but it creates or basically has on the chipset a bunch more lanes. How they are assigned are pretty similar. It might look like you have a bunch of PCIe lanes, but really you don't, you only have the 4x PCIe to the CPU. Also again the Sata doesn't have dedicated lanes. It's server directly from the Chipset and uses the resources and connection the the CPU when it needs it but doesn't have its own PCIe pathway.