If a player in survival mode is in the middle of breaking a block, and suddenly changes gamemode to adventure mode where breaking a block should not be possible, the block breaking texture progression will still play when the player holds left mouse click on the block. This does not apply to any other block in adventure mode, only the block the player was looking at when the switch happened.

In the clip, when I change to the book and quill, my gamemode is changed to survival, and when I change off of it, my gamemode is reverted back to adventure.

(Also, you can't edit books and quills when in adventure mode, just FYI)