Switching tools keeps enchantment effects for a brief second

Description:
Switching tools keeps =enchantment effects for a few moments.

Steps to reproduce:

1. Enchant a Diamond Pickaxe with Efficiency V and put it in hotbar position 1 

2. Grab an *unenchanted* Diamond Shovel and put it in hotbar position 2 

3. Place or Find a patch of Gravel/Dirt

4. In Survival Mode, begin mining the Gravel/Dirt with the Diamond Pickaxe and quickly switch to the Diamond Shovel

Note: The effect works for longer when using the mouse wheel but it also works by using the hotkeys

Expected Result:
The Gravel/Dirt is mined normally with the Diamond Shovel

Observed Result:
The Gravel/Dirt is mined instantly as if the Shovel was enchanted with Efficiency V. Sometimes 2-3 blocks of Gravel/Dirt are insta-mined