According to the 1.16.100 changelog,

• Lanterns can now be placed underwater and do not pop when a water source block is place on them

This statement does not make clear whether lanterns should pop when they touch flowing water. The way it reads to me is that emphasis is placed on source water in contradistinction to flowing water, so I expected lanterns to still break in flowing water even though they can be waterlogged, which would make them just like rails. That would make sense to me because rails are also made of pieces of iron fashioned together with other materials. However, in-game lanterns now block flowing water, which doesn't really make sense because they are small like flower pots and would be lighter than rails.

Steps to reproduce

1. Place a lantern on the ground.
2. Place water next to the lantern on a different block.

Expected result

Flowing water breaks the lantern.

Actual result

The lantern stops the flowing water.