This goes against the usual trend of mobs that drop cookable food items dropping cooked food when killed by fire.
Linked issues
relates to 6
MCPE-122492
Zombie that is killed on fire/by lava do not drop baked potatoes
Open
MC-41576
Flame zombies dont make cooked potatoes
Resolved
MC-70738
Killing guardian with lava does not give cooked fish
Resolved
MC-102269
Polar bears drop raw fish instead of cooked fish when killed with fire or lava
Resolved
MC-254922
Elder guardians that are on fire do not drop dry sponges when killed
Open
1 more links
I can confirm for 1.16.2