So basically when breaking blocks by holding the default left click (or any mouse button) there is one frame between blocks where the mouse input is ignored, this makes mining many blocks very inefficient, and when binding the break/destroy command to a keyboard, this bug is not present (Does not aplly to instamining).

Steps to Reproduce:

1) Open Menu>Options>Controls>Key binds and bind your Attack/Destroy to Left Button (Left Mouse Button) and then Done.

2) Break blocks (In survival) using any tools and look for small delays between breaking blocks.

3) Open Menu>Options>Controls>Key binds and bind your Attack/Destroy to any keyboard button and then Done.

4) Break blocks (In survival) using any tools and notice that the blocks are breaking slightly faster.

Observed Results:

When breaking many blocks this bug adds up over long periods of time, wich players do very often. 

Expected Results:

The expected result is observed when breaking blocks using any key on the keyboard instead of the default left click, this is how it is supposed to work on left click.

Screenshots/Videos:

The videos speed is not modified, I made a restone lamp clock to demonstrate that.

Also on the video I broke exacly 100 blocks (from y=156 to y=56) and used a diamond picaxe and stone to demonstrate my point.

Video 1 and 2 are the full recording, while Video 3 is a slightly cut version.

Video 1: Breaking Blocks using Left Click (Default):
https://youtu.be/G1FwK3V3AUs

Video 2: Breaking Blocks using Keyboard:
https://youtu.be/tZVA1MzCD6M

Video 3: Comparison (Side to side) of video 1 and video 2:
https://youtu.be/ioEkcUImIj8

Notes:

First of all, understand that my english is not my first language, so excuse my spelling mistakes;

I would like reinforce my point that the only edit on the video were subtitles, compressing and split screen.

This fix is a small quality of life thing, that many minecraft players will appreciate, even though they, for all this time haven't noticed this small discrepancy.