The bug

Fire resistance and Weakness potions do not spawned from ominous item spawners in Java, but can spawned in Bedrock.

I was tested and can confirmed that the fire resistance and weakness potions do not spawning in Java Edition.

How to reproduce

1. Placing some trial spawners on ground. 
2. Putting any spawn eggs in the spawners
3. Drinking an ominous bottle
4. Switching the gamemode to survival
5. Observing the projectiles falling down
6. Move to a distant location and repeat the about steps

← No fire resistance or weakness potions.

Expected behavior

The ominous item spawner have a chance to spawning fire resistance or weakness potions like Bedrock Edition.

Observed behavior

The ominous item spawner never spawning fire resistance or weakness potions.