Business PCs, Workstations and Point of Sale Systems

Hello community, I just bought a used Z2 Mini G3 Workstation and added a HP Z Turbo Drive G2 SSD (Samsung) to the M.2 slot on the motherboard. However, the SSD runs only at a fraction of the expected speed, about a quarter of what the same SSD is able to accomplish in a HP Z440 Workstation, using a HP PCie x4 adapter. Samsung Magician software reports PCIe 3.0 x4 in the Z440 and only PCie 3.0 x1 in the Z2 Mini G3. However, the Z2 Mini G3 data sheet claims PCIe 3.0 x4 for the M.2 2280 slot on the motherboard. Why it is only running at x1? I checked the BIOS but there is nothing to do, except an option to disable the M.2 slot to hide it from the OS. What needs to be done to let the SSD run at x4? It seems that all 4 lanes are physically connected to the M.2 slot but for unknown reason the SSD connects only to a single lane. Is this enforced by HP to save power in the Mini Workstation? Thanks a lot in advance!