Regarding how Framework adapted the design for the reduced number of PCIe lanes available:
Apparently in the first generation Framework Laptop 16, the m.2 2280 and m.2 2230 SSD slots both provide PCIe 4.0 x4 NVMe (x4 = 4 lanes each).
In the second generation Framework Laptop 16, the m.2 2230 slot provides PCIe 4.0 x2 NVMe (2 lanes).
Note: The secondary storage interface supports x2 PCIe 4.0. SSDs with x4 PCIe 4.0 will run at slower speed. [https://frame.work/laptop16?tab=specs ]