Recently, there was a new field added in the StartGamePacket, that goes somewhat like "ServerAuthorativeBlockBreaking". This feild allows for block breaking to be handled by the server. There is also another field that goes along the name of "PlayerMovementType". PlayerMovementType can determine wether or not movement is server authorative. However, when the PlayerMovementType feild is set to where movement is done by the server, server authorative block breaking is enabled (regardless if it's set to false in the StartGamePacket).

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Steps to reproduce:
(Server software used was PocketMine-MP, you could use any other server software and still get the same result)
1. When sending StartGamePacket, set the PlayerMovementType to 1 (or 2, doesn't matter), and ServerAuthoritativeBlockBreaking to false

2A. If you have server auth block breaking implemented, go into game and view what packets are sent - no InventoryTransaction packets are sent (they should be, considering server authorative block breaking is disabled)

or

2B (shown in video). Enjoy the unread bytes mess when breaking blocks

Video: https://streamable.com/mlls9w