The bug

When the entity inflicting the damaged in the /damage command is a some mobs, the entity target to be damaged will not receive additional status effects.

Reproduce steps and affected mobs

1. Wither skeleton

   /damage @p 1 minecraft:generic by @e[type=minecraft:wither_skeleton,limit=1] from @e[type=minecraft:wither_skeleton,limit=1]

2. Wither skeleton with bow

   /damage @p 1 minecraft:arrow by @e[type=minecraft:arrow,limit=1] from @e[type=minecraft:wither_skeleton,limit=1]

3. Husk

   /damage @p 1 minecraft:generic by @e[type=minecraft:husk,limit=1] from @e[type=minecraft:husk,limit=1]

4. Stray

   /damage @p 1 minecraft:arrow by @e[type=minecraft:arrow,limit=1] from @e[type=minecraft:stray,limit=1]

5. Cave spider

   /damage @p 1 minecraft:generic by @e[type=minecraft:cave_spider,limit=1] from @e[type=minecraft:cave_spider,limit=1]

6. Bee

   /damage @p 1 minecraft:generic by @e[type=minecraft:bee,limit=1] from @e[type=minecraft:bee,limit=1]

7. Pufferfish

   /damage @p 1 minecraft:generic by @e[type=minecraft:pufferfish,limit=1] from @e[type=minecraft:pufferfish,limit=1]

8. Burning zombies, zombie villagers and drowneds

   /damage @p 1 minecraft:generic by @e[type=minecraft:zombie,limit=1] from @e[type=minecraft:zombie,limit=1]

Expected to happen...

• When the entity inflicting the damage is a wither skeleton, the target gets the wither effect.
• When the entity inflicting the damage is a wither skeleton with bow, will cause the target to catch fire.
• When the entity inflicting the damage is a husk, the target gets the hunger effect.
• When the entity inflicting the damage is a stray, the target gets the slowness effect.
• When the entity inflicting the damage is a cave spider, bee or pufferfish, the target gets the poison effect.
• When the entity inflicting the damage is a burning zombies, zombie villagers and drowneds, will cause the target to catch fire.