In the trial spawner nbt, the ominous_config tag sets the configuration values to use in ominous mode. Any omitted values are copied from the normal_config tag. However, when any values in ominous_config are equal to the default value, they don't get saved, resulting in them being copied from normal_config on the next load.

How to reproduce:
1. Use the following command to place a custom trial spawner:

/setblock ~ ~ ~ minecraft:trial_spawner{normal_config:{spawn_potentials:[{data: {entity:{id: "zombie"}}, weight: 1}], total_mobs:1.0f},ominous_config:{total_mobs:6.0f}}

This trial spawner should have a total mobs setting of 1 in normal mode and 6 in ominous mode.
2. Drink an ominous potion and go into survival mode
3. you will indeed need to defeat 6 zombies to get the reward.
4. Go back into creative mode, break the spawner and rerun the command to reset the cooldown.
5. Optional: Use /data get block to see that ominous_config.total_mobs is not saved in nbt.
6. Close and reload the game.
7. Verify you still have the trial omen effect and go into survival mode
8. you will now only need to defeat 1 zombie to get the reward.
9. Optional: Repeat the process with a different number in ominous_config.total_mobs and verify that it does get saved properly.