Concrete powder doesn't fall.

I'm making an adventure map and I use a fill command to fill some blocks to air. Above those blocks were concrete powder blocks and when the blocks below them I expected the concrete pwoder blocks to fall down. Like it always does when I tested it in different snapshots.

What actually happened was that the concrete powder blocks were floating and didn't get updated and didn't fall.

1. Fill a row of solid non-gravity blocks.
2. Fill an area above the solid non-gravity blocks with concrete powder blocks.
3. Fill the area where the solid non-gravity blocks are with air.
4. The concrete powder still floats.