If an animal possesses the fire resistance effect, it will still yield cooked meat upon demise while ablaze. Whether this behavior is deliberate or requires consideration as a feature request is within Mojang's purview to decide. As the fire resistance effect is applicable to the mob, it could be inferred that it should also extend to the resulting meat.

Steps to reproduce

1. Summon a pig
2. Apply a fire resistance potion to it
3. Kill it using a sword enchanted with Fire Aspect

Observed: The pig dropped cooked porkchop despite having fire resistance,
Expected: The pig should drop raw meat, considering its fire resistance.