Waterlogged blocks turn lava into obsidian or cobblestone on all sides, even those water doesn't flow out of

Updated by @unknown.
Summary:
Lava converts into obsidian or cobblestone when coming into contact with waterlogged blocks even if the water doesn't visually touch the lava.

Steps to reproduce:

1. Build the setup as shown in the attachment below.

   [media]

2. Break the diamond block.

3. Take note as to whether or not lava converts into obsidian or cobblestone when coming into contact with waterlogged blocks even if the water doesn't visually touch the lava.

Observed results:
Lava converts into obsidian or cobblestone when coming into contact with waterlogged blocks even if the water doesn't visually touch the lava.

Expected results:
Lava would not convert into obsidian or cobblestone when coming into contact with waterlogged blocks when the water doesn't visually touch the lava.

Original description:
When you place lava/ when lava touches the back of a waterlogged stair where there isnt water it turns lava into cobble/obsidian. Also if the water rolls on the stair it will destroy the waterlogged stair and replace it with stone.