Superflat End with Structures

Hey everyone! I'm working on a flat End dimension datapack, but I'm having trouble getting structures to generate properly. Here's my current situation:
End Cities aren't spawning: Likely due to the isIslandChunk requirement failing in a flat world. The default the_end biome is excluded from city generation.
End Spikes (dragon fight platform) aren't generating at all: This is especially confusing since they normally generate regardless of terrain.
This is the code, flat generation and dragon fight works correctly:
{
    "type": "minecraft:the_end",
    "generator": {
        "type": "minecraft:flat",
        "settings": {
            "biome": "minecraft:the_end",
            "layers": [
                {
                    "block": "minecraft:air",
                    "height": 10
                },
                {
                    "block": "minecraft:end_stone",
                    "height": 56
                }
            ],
            "structure_overrides": [
                "minecraft:end_spike",
                "minecraft:end_city"
            ]
        }
    }
}
Thank you so much!
P.S.: This is my first datapack, and I've coded it using ChatGPT. I have already made the nether without any issues.