If water can fill cobblestone stairs, walls, slabs, nether brick fences why Cant it be filled with lava?

Only water can fill waterlogged blocks.

if water can fill why cant lava?

It took me too long to respond due to me building a bucket pixel art.

And this is my first report.

And its 4:00 in the morning for me.

And i forgot to put something in the title.