The Bug:

Lava cauldrons deal damage one tick earlier than lava. I think this is inconsistent.

Steps to Reproduce:

1. Download the provided structure block .nbt file that contains the necessary setup in order to test the problem. mc-259624.nbt
2. Create a world and place the .nbt file into the generated\minecraft\structures folder.
3. Place down a structure block with the appropriate data already inputted into it by using the command provided below.

   /setblock ~1 ~ ~1 minecraft:structure_block{ignoreEntities:0b,mode:"LOAD",name:"minecraft:mc-259624",posX:1,posY:0,posZ:1,powered:0b,showboundingbox:1b,sizeX:5,sizeY:3,sizeZ:5}

4. Open the structure block and click the "LOAD" button to load the structure.
5. Click the button on the ground and watch the creepers closely as soon as they're summoned.
6. Take note as to whether or not lava cauldrons deal damage one tick earlier than lava.

Observed Behavior:

Lava deals damage to the mob 1 tick later than the lava cauldron.

Expected Behavior:

Lava deals damage to the mob 1 tick earlier (than at the moment) so that the mobs take damage from the lava cauldron and lava at the same time.

Videos:

MC-259624 - Analysis.mp4
creeper in lava.mp4

Screenshots: