The 10k GVWR is just a different number on the sticker, compared to the equivalent higher-GVWR models (up to 11,500 pounds) with 17" wheels. In this case, the rear axle is always tire-limited to 6,340 pounds.
The 18" wheels allow a RAWR up to 6,780 pounds and those leafs are upgraded accordingly. 20" wheels allow for a 7,230 RAWR. However, Ford still offers a "GVWR Downgrade" option for these well, but to 11,400 pounds for some reason.
The axles themselves, and the brakes, are common among all GVWRs except the F450. If you had to buy a 10k GVWR truck to comply with your HOA, and need the higher payloads of the 18" or 20" wheels... Swapping wheels and adding a leaf (or airbags) is easy enough.
2020 F-Series Complete Specification PDF