The latest 1.21.0.23 Preview made the vault loot changes to match Java Edition. However, the tipped arrows from the ominous vault loot are different. On Java, it is the Arrows of Slowness IV, however on Bedrock, it is the Arrows of Slow Falling.

reward_ominous_common.json:

• Bedrock: the loot table gives 4-12 Arrows of Slow Falling.

          {
            "type": "item",
            "name": "minecraft:arrow",
            "weight": 3,
            "aux_val": 42,
            "functions": [
              {
                "function": "set_count",
                "count": {
                  "min": 4,
                  "max": 12
                }
              },
              {
                "function": "set_data",
                "data": 42
              }
            ]
          }
  

• Java: the loot table gives 4-12 Arrows of Slowness IV.

  {
            "type": "minecraft:item",
            "functions": [
              {
                "add": false,
                "count": {
                  "type": "minecraft:uniform",
                  "max": 12.0,
                  "min": 4.0
                },
                "function": "minecraft:set_count"
              },
              {
                "function": "minecraft:set_potion",
                "id": "minecraft:strong_slowness"
              }
            ],
            "name": "minecraft:tipped_arrow",
            "weight": 3
          }
  

The reason could be explained the fact that the aux value and data value for the tipped arrows are incorrect. As we can analyze, the aux value and data value is 42, which refers to the Slow Falling arrows. However, the aux value and data value for the Slowness IV arrows should be 43.

You can test which arrows by using the commands to check which arrows are correct here:
Slow Falling 30 seconds: /give @s arrow 1 42
Slowness IV: /give @s arrow 1 43