Breaking Gravel at y0 breaks 2 when near the player.

What I expected to happen was...:
I expected the gravel above to drop into place.

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What actually happened was...:
The gravel drops but the second block breaks into a gravel item.

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Steps to Reproduce:
1. Find a patch of underground gravel near the transition point of y0
2. Break the lowest gravel block (in creative insta punch) of a stack at least 3 high
3. Watch the gravel fall and give you one gravel block as the single gravel block above (2.) breaks like hitting a torch.