The bug

Dispensing a Bucket of Tadpole into a replaceable block (like grass, air, water, or lava) fails to dispense the tadpole and the water, resulting in the Bucket of Tadpole item being dispensed instead. Other types of buckets with entities properly replace the block the bucket is being used on with water.

How to reproduce

1. Place a dispenser facing a block of lava
2. Place a Bucket of Axolotl in the dispenser, and activate it
   The axolotl and water replace the block of lava
3. Place a Bucket of Tadpole in the dispenser, and activate it
   The tadpole and water fail to replace the block of lava, causing the dispenser to drop the item instead

Expected behavior

The Bucket of Tadpole would behave similar to the Bucket of Axolotl in the dispenser, and would replace replaceable blocks when being dispensed.