[MC-195468] World Generation Settings not working on dedicated server

Hi! I used Export World Generation Setting button to obtain generation settings JSON file, and then I was trying to use it in server.properties.
It does not work at all on the server - settings are not importing at all, even tho it fully works when creating a singleplayer world.

The worldgen_settings_export.json file:

{
  "bonus_chest": false,
  "dimensions": {
    "minecraft:overworld": {
      "type": "minecraft:overworld",
      "generator": {
        "settings": {
          "lakes": false,
          "features": true,
          "biome": "minecraft:the_void",
          "structures": {
            "structures": {}
          },
          "layers": [
            {
              "height": 1,
              "block": "minecraft:air"
            }
          ]
        },
        "type": "minecraft:flat"
      }
    },
    "minecraft:the_nether": {
      "type": "minecraft:the_nether",
      "generator": {
        "settings": {
          "lakes": false,
          "features": true,
          "biome": "minecraft:the_void",
          "structures": {
            "structures": {}
          },
          "layers": [
            {
              "height": 1,
              "block": "minecraft:air"
            }
          ]
        },
        "type": "minecraft:flat"
      }
    },
    "minecraft:the_end": {
      "type": "minecraft:the_end",
      "generator": {
        "settings": {
          "lakes": false,
          "features": true,
          "biome": "minecraft:the_void",
          "structures": {
            "structures": {}
          },
          "layers": [
            {
              "height": 1,
              "block": "minecraft:air"
            }
          ]
        },
        "type": "minecraft:flat"
      }
    }
  },
  "seed": 6225140477871570822,
  "generate_features": true
}

Some "server.properties" lines:

generator-settings={"bonus_chest": false,"dimensions": {"minecraft:overworld": {"type": "minecraft:overworld","generator": {"settings": {"lakes": false,"features": true,"biome": "minecraft:the_void","structures": {"structures": {}},"layers": [{"height": 1,"block": "minecraft:air"}]},"type": "minecraft:flat"}},"minecraft:the_nether": {"type": "minecraft:the_nether","generator": {"settings": {"lakes": false,"features": true,"biome": "minecraft:the_void","structures": {"structures": {}},"layers": [{"height": 1,"block": "minecraft:air"}]},"type": "minecraft:flat"}}},"seed": 6225140477871570822,"generate_features": true}
level-type=flat

Full server log from ~~MC-199659~~:

Picked up _JAVA_OPTIONS: -Dawt.useSystemAAFontSettings=on -Dswing.aatext=true 
[21:15:24] [main/ERROR]: Not a registry ops 
[21:15:24] [main/INFO]: Environment: authHost='https://authserver.mojang.com', accountsHost='https://api
.mojang.com', sessionHost='https://sessionserver.mojang.com', name='PROD' 
[21:15:24] [main/WARN]: Ambiguity between arguments [teleport, destination] and [teleport, targets] with
 inputs: [Player, 0123, @e, dd12be42-52a9-4a91-a8a1-11c01849e498] 
[21:15:24] [main/WARN]: Ambiguity between arguments [teleport, location] and [teleport, destination] wit
h inputs: [0.1 -0.5 .9, 0 0 0] 
[21:15:24] [main/WARN]: Ambiguity between arguments [teleport, location] and [teleport, targets] with in
puts: [0.1 -0.5 .9, 0 0 0] 
[21:15:24] [main/WARN]: Ambiguity between arguments [teleport, targets] and [teleport, destination] with
 inputs: [Player, 0123, dd12be42-52a9-4a91-a8a1-11c01849e498] 
[21:15:24] [main/WARN]: Ambiguity between arguments [teleport, targets, location] and [teleport, targets
, destination] with inputs: [0.1 -0.5 .9, 0 0 0] 
[21:15:24] [main/INFO]: Reloading ResourceManager: Default 
[21:15:25] [Worker-Main-10/INFO]: Loaded 7 recipes 
[21:15:25] [Worker-Main-10/INFO]: Loaded 927 advancements 
[21:15:26] [Server thread/INFO]: Starting minecraft server version 1.16.2 
[21:15:26] [Server thread/INFO]: Loading properties 
[21:15:26] [Server thread/INFO]: Default game type: SURVIVAL 
[21:15:26] [Server thread/INFO]: Generating keypair 
[21:15:26] [Server thread/INFO]: Starting Minecraft server on *:25565 
[21:15:26] [Server thread/INFO]: Using epoll channel type 
[21:15:26] [Server thread/INFO]: Preparing level "world" 
[21:15:26] [Server thread/INFO]: Preparing start region for dimension minecraft:overworld 
[21:15:27] [Server thread/INFO]: Preparing spawn area: 0% 
[21:15:27] [Server thread/INFO]: Preparing spawn area: 0% 
[21:15:27] [Server thread/INFO]: Preparing spawn area: 0% 
[21:15:28] [Server thread/INFO]: Preparing spawn area: 39% 
[21:15:29] [Worker-Main-12/INFO]: Preparing spawn area: 83% 
[21:15:29] [Worker-Main-10/INFO]: Preparing spawn area: 83% 
[21:15:29] [Worker-Main-12/INFO]: Preparing spawn area: 83% 
[21:15:29] [Worker-Main-11/INFO]: Preparing spawn area: 83% 
[21:15:30] [Worker-Main-9/INFO]: Preparing spawn area: 83% 
[21:15:30] [Worker-Main-9/INFO]: Preparing spawn area: 83% 
[21:15:31] [Worker-Main-8/INFO]: Preparing spawn area: 83% 
[21:15:31] [Worker-Main-14/INFO]: Preparing spawn area: 87% 
[21:15:32] [Worker-Main-14/INFO]: Preparing spawn area: 91% 
[21:15:32] [Server thread/INFO]: Preparing spawn area: 98% 
[21:15:33] [Server thread/INFO]: Time elapsed: 6638 ms 
[21:15:33] [Server thread/INFO]: Done (6.690s)! For help, type "help"