Referring to MC-254920 and MC-254922. Since MC-254922 is triaged, the cooking effect of burning mobs likely should apply to non-meat items. This could be viewed as a feature request akin to MC-254920, but it's ultimately up to Mojang to decide. With iron boots being smeltable into iron nuggets as of version 1.11.1, one might anticipate that a burning Piglin bartering iron boots would yield an iron nugget instead. However, this isn't currently the case.

steps to reproduce

1. Summon a group of Piglins

2. /execute as @e[type=minecraft:piglin,distance=..10] run data merge entity @s {Fire:1000}

3. /effect give @e[type=minecraft:piglin,distance=..10] minecraft:resistance infinite 4 true

4. /execute at @e[type=minecraft:piglin,distance=..10] run summon item ~ ~ ~ {Item:{id:"minecraft:gold_ingot"}}

5. Continue to execute step 4 repeatedly until you acquire iron boots enchanted with Soul Speed

Observed: The Piglin traded iron boots despite being ignited.
Expected: The iron boots are supposed to be smeltable into iron nuggets, hence yielding an iron nugget instead in this scenario.

Note: To resolve this issue, one potential solution is to incorporate a "minecraft:furnace_smelt" function into the loot table entry, under the condition that the entity is engulfed in flames.