Guardians not spawning on superflat worlds

I'm new here, but i can confirm this.
I have been messing around in superflat mode with the biomes set to deep ocean with ocean monuments spawned evereywhere, but guardians just won't spawn.
I have been trying to use ocean monuments for use in a survival map, but this kinda a big wrench in my plans.

Confirmed for 14w34d.

Confirmed in 1.8.1-pre3. Repro steps:

1. Create New World
2. Game Mode Creative
3. Seed: NoGuardians
4. World Type: Superflat
5. Customize to preset: "Water World"
6. Generate Structures: ON

You will spawn near a monument at X=1200, Z=-200. Explore the temple (Respiration Helmet and Night Vision potion recommended). You will find Elder Guardians (spawned in with the structure), but no normal guardians will spawn, only squid.

Not a dup, but possible connection to MC-3524? (Witches do not spawn in superflat worlds).

Note, this is also reproducible in a normal world by editing the map type. Repro steps:

1. Make a new, normal world in creative mode
2. Seed: 202961
3. Note the monument near spawn, X=-350, Z=150
4. Guardians will spawn when on Normal difficulty
5. Switch to peaceful and exit
6. Open the "level.dat" file in NBTExplorer.EXE
7. Edit the Data > "generatorName" value to a value of "flat"
8. Save and exit, and re-load the world in Minecraft
9. Switch back to Normal difficulty, no guardians will spawn

You can edit the type back to "normal" and Guardians will begin spawning again.

Please fix! I need this for a custom map!!

Still an issue in 1.8.2-pre7

Affects 1.13 "Aquatic Update"  I would think by now this would have been addressed considering 1.13 is so much about the water. Please consider how many are wanting to start a new water world, yet only to find ocean monuments that don't spawn guardians.

Confirmed for 1.13.1.

Confirmed for 1.14 Pre-Release 2

Confirmed for 1.14

Testing regarding this issue, this bug is superseded by issue MC-169728