As I know, only Stratix 10 DX device support the PCIe Gen4. May I know where you get the screenshot?
I can't see this table in Intel FPGA PCIe webpage - https://www.intel.com/content/www/us/en/programmable/products/intellectual-property/ip/interface-pro...
I found the table from this link - https://www.intel.com/content/www/us/en/products/programmable/fpga/stratix-10.html
By right, only Stratix 10 DX supporting Gen4. Let me clarify and get back to you later.