When breaking a block using an empty hand, or a stick, or a stone, or a cobble, ...
(in fact all non-specific tools), the result of BlockBreakEvent.getBlock().getDrops() is not always correct.

For example:

• If you break a DIAMOND_ORE, it will return DIAMOND (should be nothing)
• If you break a STONE, it will return COBBLESTONE (should be nothing)

[ FYI, BlockDropItemEvent.getItems() (deprecated event) return value is correct. ]

Read this topic for more details:
https://www.spigotmc.org/threads/blockbreakevent-getdrops-and-empty-hand.406866
(it also contains the main part of the source code of the attached testable plugin + results I got with)

How to use the attached "plugin": (to quickly test this bug)

1. Put the jar in plugins folder
2. Start the server
3. Connect to it as a player
4. Break a block
5. Read the console output

You'll see a difference between what the console say ("Result drops" = return of method BlockBreakEvent.getBlock().getDrops()) and what is effectively dropped to the ground.

• All blocks (like dirt) which could be break without a specific tools will be same.
• All blocks (like DIAMOND_ORE) which require a specific tools will differ.

You can see examples of what I've tested by extending the "spoiler" tag in the topic mentioned above.