This line of a fox's loot table:

"conditions": [
                {
                  "condition": "entity_properties",
                  "predicate": {
                    "nbt": "{HandItems:[{id:\"minecraft:wheat\"},{}],Type:\"red\",Sleeping:0b}"
                  },
                  "entity": "this"
                }

should check for a fox, holding wheat that is red and isn't sleeping. With the /loot command it works as if the mob is alive and holding the wheat. But when it is killed, it produces a different loot as the hand items are dropped before the loot table is processed. With other mobs, the hand items are consistent and can be read through the loot table to process the correct loot as the hand items are processed after the loot table instead of before.