This could be fixed by making the tallow drop a loot table and injecting that into pig loot table. (example, for dungeon loot: https://github.com/SilentChaos512/SilentGems/blob/a0a42d9a6c23d4934ce1193726b09dada585622f/src/main/java/net/silentchaos512/gems/init/GemsLoot.java )

I understand the tallow drop is defined in code so it can be configurable, but if it was a loot table this would be fixed and end users could still change it with datapacks.

Of course the code could also check for doMobLoot but imho we should use data as much as possible