Entity shadows show under the half-slab instead of on it. But my guess that the game registers the half-slab when stood on, as a partial of a full, but the game does not have a 0.5, and is rounded down.
Thank you for your report. However, your ticket has been resolved as a duplicate.
This issue has been linked to the original bugreport: MC-21024. You can find or add further information on that report. Please search before reporting any bugs, as it's likely that one exists already.
Entity shadows show under the half-slab instead of on it. But my guess that the game registers the half-slab when stood on, as a partial of a full, but the game does not have a 0.5, and is rounded down.