Block check ignores edges

[FreakyLittleGoblin]

Hi,
I am using Spawn.json to deny certain mobs that ignore natural spawning on dreadful dirt, however it is only partially effective.
Below is my code:

  //Overworld blacklist, Dreadful Dirt ignores this.
  {
    "dimension": "minecraft:overworld",
    "mod": "mutantmonsters",
    "result": "deny"
  },

  //Dreadful Dirt mob blacklist (they can still spawn on the edges)
  {
  "block": "mob_grinding_utils:dreadful_dirt",
  "mob": ["#mutantmonsters:mutants","mowziesmobs:grottol","#c:slimes","#terra_curio:slime","knightquest:ghosty"],
  "when": "finalize",
  "result": "deny"
  },

The issue:
Mobs are blocked perfectly fine when they spawn directly on the dreadful dirt.
Mobs are not blocked when spawning on the dreadful dirt when the block beside it is not Dreadful Dirt as if them barely touching air or stone or another block is enough for the rule to consider it not dreadful dirt.

[FreakyLittleGoblin]

Also unrelated but I've worked with this mod quite a bit if you would like some more examples for your wiki