If you put 2 pointed dripstone between a water / lava fountain and the cauldron, it does not fill with lava / water but the particles are there (you only see the difference with lava).
Steps to reproduce:
1. Put 2 cauldrons.
2. Put a block a few blocks on top of each cauldron.
3. Place a fountain of water / lava on the blocks.
4. In the first, place a pointed dripstone between the cauldron and the block with a water / lava fountain on top.
5. In the second, place two pointed dripstones between the cauldron and the block with a water / lava fountain on top.
Only the cauldron with a pointed dripstone fills the cauldron with water / lava. The one with two pointed dripstones shows the particles but does not fill the cauldron.
All cauldrons were filled with water / lava, no matter how many pointed dripstones there were between the fountain and the cauldron.