Custom data not working on loot pool item?

{           "type": "item",           "weight": 1,           "name": "minecraft:trial_key",           "functions": [             {               "function": "set_count",               "count": 1             },             {               "function": "set_components",               "components": {                 "minecraft:max_stack_size": 2,                 "minecraft:item_model": "insanity:figurine_fish",                 "minecraft:custom_data": {                   "mackerel": 1                 }               }             },             {               "function": "set_name",               "name": [                 {                   "color": "light_purple",                   "text": "The Uncatchable One"                 }               ],               "target": "item_name"             },             {               "function": "set_lore",               "lore": [                 {                   "color": "white",                   "italic": false,                   "text": "Lets you slip away easier when taking damage."                 },                 {                   "color": "blue",                   "italic": false,                   "text": "Cost: 3"                 }               ],               "mode": "append"             }           ]         }